tag:theconversation.com,2011:/global/topics/smell-7349/articlesSmell – The Conversation2023-09-10T13:04:13Ztag:theconversation.com,2011:article/2041642023-09-10T13:04:13Z2023-09-10T13:04:13ZThe nose knows: How microbiomes and the smells they produce help shape behaviour in bugs, birds, beasts and humans<figure><img src="https://images.theconversation.com/files/547261/original/file-20230908-27-yeuep5.jpg?ixlib=rb-1.1.0&rect=612%2C68%2C4958%2C3759&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">The microbiome functions as an 'invisible organ' but it often makes its presence known by emitting sounds and smells.</span> <span class="attribution"><span class="source">(Shutterstock)</span></span></figcaption></figure><iframe style="width: 100%; height: 100px; border: none; position: relative; z-index: 1;" allowtransparency="" allow="clipboard-read; clipboard-write" src="https://narrations.ad-auris.com/widget/the-conversation-canada/the-nose-knows-how-microbiomes-and-the-smells-they-produce-help-shape-behaviour-in-bugs-birds-beasts-and-humans" width="100%" height="400"></iframe>
<p>Microbes are an integral part of most, if not all multi-cellular organisms. In fact, these organisms are the way they are because of the tiny partners they house within and on them. These microbes constitute the microbiome: an “invisible organ” weighing approximately <a href="https://doi.org/10.1007/978-981-10-7684-8">2.5 to three kilograms</a> in an adult human and much more in larger animals.</p>
<p>This unique body part was made visible with the advent of modern molecular imaging technologies. In my book <em><a href="https://www.routledge.com/Microbiomes-and-Their-Functions-Why-Organisms-Need-Microbes/Appanna/p/book/9780367749897">Microbiomes and their Functions</a></em>, I explore how it works in partnership with other visible organs and engages in a variety of physiological functions essential for the development and survival of the hosts. </p>
<p>Microbiomes have been part of all these organisms from the beginning, and have evolved in tandem with them, just as their visible organs have.</p>
<p>The digestive tract, with all its components, is a good example of how organs can be shaped by their microbial inhabitants. The digestive tract has markedly disparate features in a carnivore, an omnivore or a herbivore. Herbivores have the longest digestive tracts and <a href="https://opentextbc.ca/biology/chapter/15-1-digestive-systems/">carnivores have the shortest</a>.</p>
<h2>The microbiome</h2>
<p>The bulk of microbiome is found in the <a href="https://doi.org/10.1007/978-981-10-7684-8_2">digestive tract</a>, where it helps extract nutrients from our diet. The diverse microbes constituting the microbiome not only contribute to optimal digestion, but also help prime our immune system, and produce hormones and neurotransmitters (or their precursors) that have profound influence on our behaviours.</p>
<p>The information-laden molecules generated by the microbiome play a crucial role in the body’s <a href="https://doi.org/10.3389/fimmu.2020.00700">non-verbal communication</a>. These <a href="https://doi.org/10.1038/s41467-020-18871-1">microbiome-derived signals</a> can elicit a range of responses including hunger, satiety (feeling full), mood changes and social behaviour.</p>
<figure class="align-right ">
<img alt="Human silhouette showing the gut-brain connection" src="https://images.theconversation.com/files/547017/original/file-20230907-29-lkr7n3.png?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/547017/original/file-20230907-29-lkr7n3.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=796&fit=crop&dpr=1 600w, https://images.theconversation.com/files/547017/original/file-20230907-29-lkr7n3.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=796&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/547017/original/file-20230907-29-lkr7n3.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=796&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/547017/original/file-20230907-29-lkr7n3.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=1000&fit=crop&dpr=1 754w, https://images.theconversation.com/files/547017/original/file-20230907-29-lkr7n3.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=1000&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/547017/original/file-20230907-29-lkr7n3.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=1000&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">The information network between the gut microbiome and the brain is aided by the vagus nerve that connects these two organs.</span>
<span class="attribution"><span class="source">(Shutterstock)</span></span>
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<p>The information network between the gut microbiome and the brain is aided by the vagus nerve that <a href="https://routledge.pub/Microbiomes-and-Their-Functions">connects these two organs</a>.</p>
<p>Microbes like Lactobacillus and Bifidobacterium residing in the gut secrete neurotransmitters known to influence human behaviour <a href="https://doi.org/10.3390/cimb44040096">such as GABA</a> (gamma-aminobutyric acid), acetylcholine, norepinephrine, oxytocin and indole metabolites. Indole derivatives are obtained when gut microbes metabolize the essential amino-acid, tryptophan.</p>
<p>For instance, the <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4449495">neurotransmitter dopamine</a> is considered a “feel good” hormone and is often associated with positive emotions. However, low levels of this molecule may contribute to anxiety. On the other hand, indoles are linked to satiety, resulting in a tendency to eat less, and are associated with weight loss.</p>
<h2>Smelly signals</h2>
<p>Despite its invisible nature, the microbiome often makes its presence known by emitting sounds and smells. The latter can be powerful signals that can influence behaviour.</p>
<p>These smelly signals can, at a distance or at a close range, prompt happiness, enthusiasm, anxiety, attraction, fear or <a href="https://doi.org/10.1007/978-981-10-7684-8">aggression</a>. The microbially-concocted odours are a very important tool in the communication arsenal that most organisms — including humans — rely on to send or receive non-verbal messages.</p>
<p>The human skin is home to a diverse range of microorganisms known to contribute to different odours. Bacteria like Staphylococcus and Corynebacterium lodge in the warm and moist underarm region of the skin where the apocrine glands, a source of chemicals, abound. The resident bacteria use these chemical nutrients to shape <a href="https://asm.org/Articles/2021/December/Microbial-Origins-of-Body-Odor">body odour</a>.</p>
<p>These apocrine glands generally produce odourless compounds. It is microbes that fashion those compounds into smell signatures characteristic of an individual. These odoriferous signals can serve to attract or repel people and modify social behaviours. For instance, the presence of select bacteria is known to process non-smelly steroids into compounds with a characteristic urine odour, not conducive to making friends. </p>
<h2>Chemical signals in animals, birds, plants, fungi</h2>
<p>In other mammals, odoriferous compounds like trimethylamine or pentanoic acid entice mates, while in animals endowed with a scent pouch, they lure prey, defend or mark territories. Some of the <a href="https://doi.org/10.3389/fevo.2017.00143">pungent chemicals</a> are notoriously reputed to keep <a href="https://www.washingtonpost.com/lifestyle/kidspost/whats-that-smell-for-some-animals-their-stink-helps-keep-them-alive/2018/08/13/9058fc62-9678-11e8-810c-5fa705927d54_story.html">predators at bay</a>. </p>
<p>Birds have a special gland that hosts a diverse microbial population, which generates scent-releasing chemicals. These easily transmittable signals are aimed at repelling predators, attracting mates, recognizing kin, promoting parental care and <a href="https://www.nytimes.com/2019/11/10/science/birds-smell-bacteria.html">identifying proprietary nests</a>.</p>
<figure class="align-center ">
<img alt="A man's hand holding a small shovel with a truffle on it, patting his truffle-hunting dog with his other hand" src="https://images.theconversation.com/files/547027/original/file-20230907-19-ya50zw.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/547027/original/file-20230907-19-ya50zw.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/547027/original/file-20230907-19-ya50zw.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/547027/original/file-20230907-19-ya50zw.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/547027/original/file-20230907-19-ya50zw.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/547027/original/file-20230907-19-ya50zw.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/547027/original/file-20230907-19-ya50zw.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Truffles — the highly sought-after edible fungus — recruit select microbes to generate aromatic alcohols that lure small mammals to dig them up, which promotes the dispersal of the truffle’s spores.</span>
<span class="attribution"><span class="source">(Shutterstock)</span></span>
</figcaption>
</figure>
<p>These smelly marks are also key to maintaining the social order of numerous insects. <a href="https://doi.org/10.1186/s40168-018-0588-z">These scents</a> can not only help camouflage the hosts, but can also convert loners to crowd-lovers. For instance, it is a scent that cajoles the solitary <a href="https://doi.org/10.3390/insects11100655">locust</a> into a gregarious lifestyle during the feeding season and triggers an insatiable appetite for vegetation.</p>
<p>Some fungi are known to enlist the fragrance of vapour-like chemicals to assemble their microbiome, which in turn helps the host perform a variety of essential physiological functions.</p>
<p>Truffles — the highly sought-after edible fungus — are renowned for their distinctive smell, but they may be dependent on the microbiome to produce this sweet fragrance. In fact, <a href="https://doi.org/10.1128/aem.01098-15">truffles recruit select microbes</a> to generate aromatic alcohols that lure small mammals to dig them up, which promotes the dispersal of the truffle’s spores.</p>
<p>Plants and algae are also dependent on microbe-derived odour prompts to assist them to survive, and even die and be scavenged. Plants depend on these smell signatures to communicate dangers lurking in their environment and even to fend off insects, birds or <a href="https://doi.org/10.3389/fmicb.2021.772420">other predators</a>.</p>
<p>When some algae bloom beyond control due to environmental conditions, they plot their own demise with the <a href="https://doi.org/10.1201/9781003166481">assistance of microbes</a>. Some of these microbes not only help the algae die, but are also responsible for producing distinctive odours that are detected and decoded as food by birds and fish. The result is a clean-up of the dead algae by feasting birds and fish.</p>
<p>The microbiome and its signature smells are crucial for most organisms, whether human, insect or plant. The silent signals sent by the microbiome are essential communications that influence behaviour, and have evolved to help the host survive and thrive.</p><img src="https://counter.theconversation.com/content/204164/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Vasu Appanna receives / has received funding from NATO, NSERC, NOHFC and FEDNOR</span></em></p>The microbiome and its signature smells are crucial for most organisms, whether human, insect or plant. The silent signals sent by the microbiome are essential communications that influence behaviour.Vasu Appanna, Professor, Biochemistry, Laurentian UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2038312023-09-04T12:16:58Z2023-09-04T12:16:58ZHow do flies find every stinky garbage dumpster? A biologist explains their sensory superpower<figure><img src="https://images.theconversation.com/files/538392/original/file-20230719-17-hhlu4f.jpg?ixlib=rb-1.1.0&rect=70%2C60%2C6619%2C4406&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">The blow fly's antenna is a specialized organ that helps the fly detect food quicker than its competitors. </span> <span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/photo/gold-fly-on-food-royalty-free-image/1170893429?adppopup=true">heckepics/iStock via Getty Images </a></span></figcaption></figure><figure class="align-left ">
<img alt="" src="https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=293&fit=crop&dpr=1 600w, https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=293&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=293&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=368&fit=crop&dpr=1 754w, https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=368&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=368&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
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<p><em><a href="https://theconversation.com/us/topics/curious-kids-us-74795">Curious Kids</a> is a series for children of all ages. If you have a question you’d like an expert to answer, send it to <a href="mailto:curiouskidsus@theconversation.com">curiouskidsus@theconversation.com</a>.</em></p>
<hr>
<blockquote>
<p><strong>How do the green-and-blue flies find stinky garbage dumpsters during the summer heat? Joey, 10, Wausau, Wisconsin</strong></p>
</blockquote>
<hr>
<p>How is it that a fly always seems to be buzzing around your food moments after you sit down for an outdoor meal?</p>
<p>The answer is practice. Or, more specifically: evolution. Flies and other insects have been on a multimillion-year journey of evolution, honing their ability to detect food. Being able to zero in on nutritious meals is a matter of life and death. </p>
<p>The family of flies <a href="https://science.iupui.edu/biology/research/faculty-labs/picard-lab/index.html">that I study</a> – the blow flies – are the buzzing ones that are usually a beautiful metallic blue, with bronze and green colors. They’ve perfected their ability to quickly sense the smells that naturally come off picnics and trash cans because they are a source of food for their offspring, also known as <a href="https://www.britannica.com/science/maggot-insect-larva">maggots</a>. </p>
<p>There is a lot of competition for a resource like an overflowing dumpster because of how nutritious garbage, and the meat that is rotting in it, is. But the blow flies can sense these odors long before their competitors or people can, and tend to <a href="https://www.theguardian.com/science/2010/sep/23/flies-murder-natural-history-museum">show up to the scene first</a>. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/538065/original/file-20230718-27-j1dmtd.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Fly eats meat." src="https://images.theconversation.com/files/538065/original/file-20230718-27-j1dmtd.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/538065/original/file-20230718-27-j1dmtd.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/538065/original/file-20230718-27-j1dmtd.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/538065/original/file-20230718-27-j1dmtd.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/538065/original/file-20230718-27-j1dmtd.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/538065/original/file-20230718-27-j1dmtd.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/538065/original/file-20230718-27-j1dmtd.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Flies’ antennae help them track down food from far distances.</span>
<span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/photo/adult-greenbottle-fly-royalty-free-image/1406254324?phrase=flies%2Beating%2Bmeat">ViniSouza128/iStock via Getty Images</a></span>
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<h2>How do flies know where to go?</h2>
<p>Sensing systems differ depending on the insect and species. The blow flies’ main sensing organ is their <a href="https://en.wikipedia.org/wiki/Antenna_(biology)">antennae</a>, two thin projections from the head that are covered in tiny hairs. These fine hairs are made up of special cells that contain <a href="https://doi.org/10.1007/s00253-011-3417-x">receptors for specific odors</a>. </p>
<p>Think about a batch of chocolate chip cookies fresh from the oven. You can detect their delicious scent because we humans have receptors on the surfaces of the cells that line the inside of our noses. These receptors send signals to the brain: yummy food ahead. They’re detecting the sweet smell of sugar-based molecules, an energy-rich food source for us. </p>
<p>What’s a “good” or a “bad” odor can differ depending on the animal doing the smelling. The enticing rotting meat stench that a fly finds delightful is perceived quite differently by a person passing by a stinking dumpster on a hot day.</p>
<p>But any fly that can detect the useful odor signal, which means “nutritious fly food here,” will have an advantage. Over time, the insects that have the receptors for those scents will have better survival rates and produce more offspring.</p>
<p>Not all smells are good, though, and being able to smell something bad can also protect whoever is sniffing it – whether that’s you or an insect. Think of the skunk spray warning smell. It won’t necessarily harm you, but it lets you know to avoid its source. </p>
<figure class="align-center ">
<img alt="A fly has detected a piece of dessert." src="https://images.theconversation.com/files/533741/original/file-20230623-23-6np9vj.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/533741/original/file-20230623-23-6np9vj.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=381&fit=crop&dpr=1 600w, https://images.theconversation.com/files/533741/original/file-20230623-23-6np9vj.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=381&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/533741/original/file-20230623-23-6np9vj.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=381&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/533741/original/file-20230623-23-6np9vj.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=479&fit=crop&dpr=1 754w, https://images.theconversation.com/files/533741/original/file-20230623-23-6np9vj.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=479&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/533741/original/file-20230623-23-6np9vj.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=479&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Flies can sense odors long before humans and their competitors can.</span>
<span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/photo/spoiled-dessert-royalty-free-image/1125293670?phrase=fly+insect+food&adppopup=true">Boris SV/Moment via Getty Images</a></span>
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<h2>Providing for offspring</h2>
<p>For more than 15 years, I’ve traveled to different parts of the world, where I expose rotten meat and <a href="https://science.iupui.edu/biology/research/faculty-labs/picard-lab/index.html">wait for flies to appear</a>. My research is related to understanding how an environment influences a fly’s ability to search for and find its food source, its sole purpose of living. For example, flies rely on wind to carry scents across varying environments. </p>
<p>Warmer temperatures promote fly activity because they’re <a href="https://en.wikipedia.org/wiki/Poikilotherm">poikilothermic</a> – meaning cold-blooded – and need heat to warm up their muscles for flight. <a href="https://theconversation.com/flies-evade-your-swatting-thanks-to-sophisticated-vision-and-neural-shortcuts-187051">Flies use visual cues</a> to fly through the air and to avoid obstacles, so they’re more active during the daytime.</p>
<p>Blow flies can <a href="https://doi.org/10.1146/annurev.en.10.010165.000403">travel up to 28 miles for food</a>. Most of the time when I expose a stinky rotten meat bait, a large group of flies <a href="https://www.youtube.com/shorts/FZnHA4U0NJM">will come right away</a>. But other times I’m surprised when no flies come to enjoy the gross buffet I’ve prepared.</p>
<p>When a female fly smells something that might be a good food source for her babies, she lands on it and assesses whether there’s enough to support her 400 or so eggs. A mom fly’s ability to smell out a good nursery for her offspring is the key to the survival of the species and ultimately why this sense is so strong. </p>
<p>Male flies are less interested in these smells as a sign of food. But since they can signal where to find female flies for mating, males will still respond to the scent of a steaming dumpster.</p>
<p>Flies have evolved to be superior garbage-smellers because this superpower helps them survive. The reason they manage to find dumpsters wherever they exist is the same reason they’ll show up to your picnic to check what’s on the menu – they’re sniffing for sustenance that will help them create the next generation of flies. </p>
<hr>
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<p class="fine-print"><em><span>Christine Picard receives funding from the National Science Foundation, the National Geographic Society, the National Institute of Justice, and the US Department of Defense. </span></em></p>Flies often beat out competitors for food because of their specialized sensing organs called antennae.Christine Picard, Associate Professor of Biology, Indiana UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2046032023-05-25T12:05:44Z2023-05-25T12:05:44ZDoctor dog: how our canine companions can help us detect COVID and other diseases<figure><img src="https://images.theconversation.com/files/527561/original/file-20230522-19-4n9lay.jpg?ixlib=rb-1.1.0&rect=9%2C9%2C6221%2C4138&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/blurred-portrait-dog-park-1999027475">Renko Aleks/Shutterstock</a></span></figcaption></figure><p>While we humans generally experience the world through sight, <a href="https://www.sciencedirect.com/science/article/pii/S0168159122002830">dogs use scent</a> to learn about the environment around them. What their nose knows is crucial for finding food, mates and safe spaces. </p>
<p>Our furry friends can also use their sniffing power to learn how people <a href="https://link.springer.com/article/10.1007/s10071-011-0386-5">are feeling</a>. For example, they can <a href="https://www.epilepsybehavior.com/article/S1525-5050(21)00312-7/fulltext">detect the scent of fear</a> in human sweat.</p>
<p>Given this, it’s perhaps not surprising that pooches’ super-smelling skills can extend to monitoring human health – including, potentially, by detecting infectious diseases such as COVID. In a <a href="https://jamanetwork.com/journals/jamapediatrics/fullarticle/2804205">recent study</a> undertaken in Californian schools, dogs were found to detect the virus with 95% sensitivity in a controlled laboratory setting and 83% in schools.</p>
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Read more:
<a href="https://theconversation.com/human-catches-covid-from-a-cat-heres-why-this-new-evidence-is-not-cause-for-panic-186233">Human catches COVID from a cat – here's why this new evidence is not cause for panic</a>
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<p>The <a href="https://anatomypubs.onlinelibrary.wiley.com/doi/10.1002/ar.20592">olfactory capability</a> of dogs far exceeds our own. Estimates suggest that dogs’ smelling ability might be <a href="https://vcahospitals.com/know-your-pet/how-dogs-use-smell-to-perceive-the-world">up to 10,000 times better than ours</a>, thanks to having more than <a href="https://doi.org/10.1016/j.lmot.2013.02.002">100 million scent receptors</a> in their nose (compared to six million in people). Dogs can detect a wide range of different smells at much lower concentrations than humans or even <a href="https://www.mdpi.com/2076-2615/11/8/2463">hi-tech laboratory instruments</a> – sometimes as low as at <a href="https://www.frontiersin.org/articles/10.3389/fvets.2016.00047/full">one part per trillion</a>.</p>
<p>Interestingly, dogs use their nostrils separately. They start sniffing <a href="https://doi.org/10.1016/j.anbehav.2011.05.020">with their right nostril</a>, and if the smell is familiar and “safe”, they switch to using their left nostril.</p>
<p>Dogs differ in the <a href="https://www.mdpi.com/2076-2615/12/4/517">shape and size of their noses</a>, of course, but all have an impressive ability <a href="https://psycnet.apa.org/doiLanding?doi=10.1037%2Fa0039271">to detect scent</a> in a range of situations. And not only are dogs good at sniffing, they love to do it. Allowing dogs to sniff can actually <a href="https://www.sciencedirect.com/science/article/abs/pii/S0168159118304325?via%3Dihub">improve their welfare</a> and make them more optimistic.</p>
<h2>Pandemic partners</h2>
<p>Dogs have shown they can accurately identify a variety of infectious diseases via scent. For example, children infected with <a href="https://www.thelancet.com/journals/laninf/article/PIIS1473-3099(19)30220-8/fulltext">malaria parasites</a> were successfully identified by dogs sniffing their foot odour. Dogs can also detect <a href="https://academic.oup.com/ofid/article/3/2/ofw051/2399288?login=false">bacterial urinary tract infections</a>, and gastrointestinal infections caused by the bacteria <a href="https://academic.oup.com/ofid/article/5/8/ofy179/5056931?login=false"><em>Clostridium difficle</em></a>, which can be <a href="https://www.gynecologiconcology-online.net/article/S0090-8258(16)31580-3/fulltext">life-threatening in vulnerable patients</a>.</p>
<p>Early in the COVID pandemic, it became clear that there was a need for extensive, real-time, accurate <a href="https://www.nature.com/articles/s41576-021-00360-w">detection of infection</a>. Respiratory infections cause the release of a range of substances that each have their own distinct smell.</p>
<p>Given dogs’ success in detecting <a href="https://www.frontiersin.org/articles/10.3389/fvets.2016.00047/full">other infectious diseases</a>, the potential role of dogs as “lab partners” during the pandemic was quickly explored.</p>
<p>Initial research revealed that after just one week of training on COVID-specific odour, dogs were able to identify infections in bodily fluids from the respiratory system, correctly identifying positive cases <a href="https://bmcinfectdis.biomedcentral.com/articles/10.1186/s12879-020-05281-3">83% of the time</a>. Once trained on respiratory samples, dogs were also capable of generalising their COVID detection skills to <a href="https://doi.org/10.1186/s12879-021-06411-1">other bodily fluids</a>, such as sweat and urine.</p>
<p>The potential for real-time screening with a high degree of sensitivity offers several advantages over traditional COVID testing methods, such as lateral flow and <a href="https://www.gov.uk/get-coronavirus-test">PCR</a> testing, including cost and efficiency.</p>
<h2>Screening by sniffing</h2>
<p>In the <a href="https://jamanetwork.com/journals/jamapediatrics/fullarticle/2804205">recent study</a>, two dogs already trained to detect the scent of COVID in the lab were taken into 27 Californian schools and completed 3,897 screenings, mostly among students, by sniffing their ankles and feet. For comparison and to check accuracy of detection, participants also undertook lateral flow tests. </p>
<p>After initial training, the dogs were detecting the virus in the lab with 95% sensitivity (correctly identifying positive cases) and 95% specificity (correctly identifying those who did not have COVID). </p>
<p>Screening people directly saw a slight drop in sensitivity to 83% and specificity to 90%. This is slightly lower than <a href="https://www.healthline.com/health/binax-now-covid-test-reviews">some estimates</a> of the sensitivity and specificity of lateral flow tests, though their reported effectiveness has varied in different studies and between tests. </p>
<p>But even considering that the dogs made a small number of errors, given that screening could be completed within seconds, efficiency was high.</p>
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<img alt="A woman sits with her dog on the couch." src="https://images.theconversation.com/files/527566/original/file-20230522-23-7thnym.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/527566/original/file-20230522-23-7thnym.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/527566/original/file-20230522-23-7thnym.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/527566/original/file-20230522-23-7thnym.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/527566/original/file-20230522-23-7thnym.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/527566/original/file-20230522-23-7thnym.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/527566/original/file-20230522-23-7thnym.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
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<span class="caption">Dogs have far superior olfactory skills compared with their human companions.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/woman-cuddles-plays-her-dog-home-1688988094">MT-R/Shutterstock</a></span>
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<p>In the same way that dogs routinely screen people for substances such as <a href="https://www.researchgate.net/profile/Clare-Browne/publication/261663456_The_use_of_scent-detection_dogs/links/00b7d534f1bf649291000000/The-use-of-scent-detection-dogs.pdf">drugs or explosives</a> as part of safety and security measures, they could offer effective medical screening services too. In high throughput environments such as schools or colleges, fast and effective screening would have distinct advantages.</p>
<p>However, all medical and health technology needs to be thoroughly evaluated for safety, cost and effectiveness, as well as any legal and ethical implications. Widespread health screening <a href="https://journals.uco.es/index.php/pet/article/view/10785">using dogs</a> similarly requires ongoing review and careful consideration, while also ensuring the welfare of the dogs. </p>
<h2>Doctor dog?</h2>
<p>COVID is just <a href="https://www.clinicalmicrobiologyandinfection.com/article/S1198-743X(19)30591-9/fulltext">one medical condition</a> our canine companions could potentially help detect. </p>
<p>Along with infectious diseases, they have successfully detected certain forms of <a href="https://doi.org/10.1186/1471-2407-13-396">cancer</a> in <a href="https://www.tandfonline.com/doi/full/10.3109/0284186X.2013.819996">biological samples</a>, the onset of <a href="https://www.nature.com/articles/s41598-019-40721-4">epileptic seizures</a>, and <a href="https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0210092">hypoglycemia</a> (low blood sugar) in diabetes patients.</p>
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Read more:
<a href="https://theconversation.com/were-wolves-dependent-on-humans-long-before-they-became-mans-best-friend-49390">Were wolves dependent on humans long before they became man’s best friend?</a>
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<p>Dogs and humans have <a href="https://theconversation.com/were-wolves-dependent-on-humans-long-before-they-became-mans-best-friend-49390">lived together for thousands of years</a>, and dogs have become constant human companions in many parts of the world.</p>
<p>The fact that they love to sniff, and are so good at it, has also made them important working partners in <a href="https://www.nature.com/articles/s41598-021-96450-0">a range of roles</a>. Using their innate skills to support human health and wellbeing through medical detection might be another way by which the human-dog relationship is deepened.</p><img src="https://counter.theconversation.com/content/204603/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Jacqueline Boyd is affiliated with The Kennel Club (UK) through membership, as Chair of the Activities Health and Welfare Subgroup, member of the Dog Health Group and Chair of the Heelwork to Music Working Party. Jacqueline also writes, consults and coaches on canine matters on an independent basis in addition to her academic affiliation.</span></em></p>Dogs love to sniff, and they’re good at it.Jacqueline Boyd, Senior Lecturer in Animal Science, Nottingham Trent UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2020422023-05-23T20:11:20Z2023-05-23T20:11:20ZHow to fool a mouse: ‘chemical camouflage’ can hide crops and cut losses by over 60%<figure><img src="https://images.theconversation.com/files/525305/original/file-20230510-15-ol6krl.jpg?ixlib=rb-1.1.0&rect=40%2C0%2C4500%2C2997&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><span class="source">Shutterstock</span></span></figcaption></figure><p>For as long as humans have grown our own food, we have battled pest animals that destroy crops and take food for themselves. </p>
<p>The traditional approach has been to try to kill the pests, typically with poisons. Too often, however, this fails to kill enough pests, harms native animals, and only minimally reduces damage.</p>
<p>We tackled this problem in a different way by asking: how do we stop hungry animals finding our crops in the first place?</p>
<p>In a <a href="https://www.nature.com/articles/s41893-023-01127-3">research paper published today</a>, we show how “chemical camouflage” can prevent house mice finding newly sown wheat seeds. The method reduced mouse damage to wheat crops by more than 60% even during plague conditions, without killing a single mouse. </p>
<h2>The rodent menace</h2>
<p>Rodents are responsible for an <a href="https://onlinelibrary.wiley.com/doi/10.1002/ps.1718">estimated 70 million tonnes of grain</a> lost worldwide each year. Even a 5% reduction in these losses could feed more than 280 million people.</p>
<p>In Australia, the 2021 mouse plague cost farmers in New South Wales alone upwards of $1 billion, according to an <a href="https://www.nswfarmers.org.au/NSWFA/Posts/Media_Releases/mr.39.21.aspx">industry association estimate</a>. A mouse plague occurs somewhere in Australia at least every four years. </p>
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<a href="https://theconversation.com/no-one-ever-forgets-living-through-a-mouse-plague-the-dystopia-facing-australian-rural-communities-explained-by-an-expert-159339">‘No one ever forgets living through a mouse plague’: the dystopia facing Australian rural communities, explained by an expert</a>
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<p>Currently, the only management option to reduce mouse numbers is broad-scale baiting. However, baiting is often ineffective and has led to calls for more lethal poisons, which carry <a href="https://theconversation.com/mouse-plague-bromadiolone-will-obliterate-mice-but-itll-poison-eagles-snakes-and-owls-too-160995">major risks for native wildlife</a>. </p>
<p>The relationship between baiting effort and crop yield is not well understood, and mouse numbers typically crash in plague years even without intervention. A better approach is to focus on reducing mouse impacts, rather than mouse numbers.</p>
<h2>How to fool a mouse</h2>
<p>Mouse damage to Australia’s most valuable crop, wheat, occurs mostly in the two-week period between sowing and germination. During this time, mice are attracted to the smell of the wheat germ – the nutritious and fatty part of the seed – beneath the ground, and they learn to dig up seeds with pinpoint accuracy, leading to significant crop losses. </p>
<p>This led to our question: can we hide the seeds so mice can’t find them?</p>
<p>Like many animals, mice primarily use their sense of smell to find food. The world is full of odours, and hungry foragers must prioritise important smells and disregard useless ones. </p>
<p>When a food is too difficult to find, or an odour is not a useful indicator of food, foragers must <a href="https://besjournals.onlinelibrary.wiley.com/doi/10.1111/j.1365-2656.2011.01817.x">give up and search for something else</a> to avoid wasting energy. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/527159/original/file-20230519-23-shy35f.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/527159/original/file-20230519-23-shy35f.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/527159/original/file-20230519-23-shy35f.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=390&fit=crop&dpr=1 600w, https://images.theconversation.com/files/527159/original/file-20230519-23-shy35f.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=390&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/527159/original/file-20230519-23-shy35f.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=390&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/527159/original/file-20230519-23-shy35f.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=490&fit=crop&dpr=1 754w, https://images.theconversation.com/files/527159/original/file-20230519-23-shy35f.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=490&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/527159/original/file-20230519-23-shy35f.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=490&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
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<span class="caption">How mice find wheat germ – and how camouflage can keep them away.</span>
<span class="attribution"><a class="source" href="https://www.nature.com/articles/s41893-023-01127-3">Parker et al. / Nature Sustainability</a>, <span class="license">Author provided</span></span>
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<p>Because hungry animals can’t afford to waste effort on odours that don’t lead to food, they are vulnerable to <a href="https://esajournals.onlinelibrary.wiley.com/doi/full/10.1002/fee.2534">olfactory misinformation and chemical camouflage</a>. As with visual camouflage, if the background, in this case smell, appears the same as the item we are trying to hide, the target item cannot be distinguished.</p>
<p>Animals can also learn about the usefulness of information, making them vulnerable to another form of misinformation – odour pre-exposure. By deploying food odours before food is available, foragers initially attracted to the odour repeatedly receive no reward and learn to ignore it. </p>
<p>When the food does become available, foragers don’t follow the odours because they know they’re unrewarding. We recently used this technique to dramatically improve nest survival for threatened shorebirds at risk from by predation by invasive predators in New Zealand.</p>
<h2>A test under tough conditions</h2>
<p>Until now, these techniques have been tested on relatively widely dispersed food items with fewer foragers over a larger area. Whether olfactory misinformation could protect a crop with more than 300 mice and 1.6 million seeds per hectare was unclear.</p>
<p>We worked on a 27-hectare wheat paddock in southwest NSW, using 60 plots to test our two olfactory misinformation techniques. We used wheat germ oil to provide the odour background, as it is made from the part of wheat seeds that mice seek out and is a relatively cheap byproduct of the wheat-milling process. </p>
<p>Both techniques involved spraying a fine mist of wheat germ oil solution onto the plots. Each application was equivalent to the smell of around 50 times the number of seeds on the plot.</p>
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Read more:
<a href="https://theconversation.com/scientists-used-fake-news-to-stop-predators-killing-endangered-birds-and-the-result-was-remarkable-152320">Scientists used 'fake news' to stop predators killing endangered birds — and the result was remarkable</a>
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<p>Our first technique, odour camouflage, began immediately after the crop was planted and was reapplied several times until seedlings appeared. This created a blanket of wheat odour to hide seeds from detection. </p>
<p>Our second technique, odour pre-exposure, had wheat germ oil applied six days before the wheat crop was planted and continued for the week after. We predicted that mice attracted to the odour before seeds were planted would begin to ignore wheat odour after repeatedly finding no seeds.</p>
<p>We also had three control treatments: one sprayed with canola oil to control for an oil effect, one we walked on without spraying to control for seed loss due to trampling, and one that remained totally untouched.</p>
<p>One and two weeks after sowing, we counted mouse damage in the form of diggings where seeds had been extracted by mice. After two weeks, we also estimated the number of seedlings that were lost to mice. The results were staggering.</p>
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<a href="https://images.theconversation.com/files/525536/original/file-20230511-15-dajgjd.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A photo of small holes dug in the ground among rows of grassy plants." src="https://images.theconversation.com/files/525536/original/file-20230511-15-dajgjd.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/525536/original/file-20230511-15-dajgjd.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/525536/original/file-20230511-15-dajgjd.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/525536/original/file-20230511-15-dajgjd.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/525536/original/file-20230511-15-dajgjd.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/525536/original/file-20230511-15-dajgjd.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/525536/original/file-20230511-15-dajgjd.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=566&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
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<span class="caption">The scene of the crime: small holes dug by mice hunting for wheat seeds.</span>
<span class="attribution"><span class="source">Peter Banks</span>, <span class="license">Author provided</span></span>
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<p>After two weeks, our camouflage and pre-exposure treatments had reduced mouse damage by 63% and 74% respectively, compared to the control. We also estimated that 53% and 72% fewer seedlings, respectively, were lost to mice on these plots. </p>
<p>The difference in the effect of pre-exposure to wheat odour and the effect of camouflage treatments was not statistically significant, and we concluded the camouflage effect is the most likely reason for the reduction in damage.</p>
<h2>Working with the animals</h2>
<p>In an increasingly populated world where food security is becoming a priority, we need new ways to tackle pest problems sustainably and safely. </p>
<p>Our methods are simple, safe and highly effective, even during a mouse plague. They carry no risks for native wildlife and involve no killing. Mice don’t go hungry either – they simply eat the foods they ate before the wheat was planted. </p>
<p>We believe simple behavioural interventions like ours, which work with animals’ motivations rather than against them, are the way of the future in wildlife management and conservation.</p>
<p>We believe this new approach has the potential to manage pest impacts without the side effects that come from using lethal pest control.</p><img src="https://counter.theconversation.com/content/202042/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Finn Cameron Gillies Parker receives funding from the Australian Research Council. </span></em></p><p class="fine-print"><em><span>Catherine Price receives funding from the Australian Research Council. </span></em></p><p class="fine-print"><em><span>Jenna Bytheway receives funding from the Australian Research Council. </span></em></p><p class="fine-print"><em><span>Peter Banks receives funding from the Australian Research Council and The Hermon Slate Foundation. He is an external member of CSIRO's Rodent Research Advisory Panel </span></em></p>Rodents destroy around 70 million tonnes of grain each year. What if we could trick them into looking elsewhere for their food?Finn Cameron Gillies Parker, PhD candidate, University of SydneyCatherine Price, Discovery Early Career Research Fellow, University of SydneyJenna Bytheway, Senior Research Officer in Conservation Biology, University of SydneyPeter Banks, Professor of Conservation Biology, School of Life and Environmental Sciences, University of SydneyLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2039052023-05-08T20:10:57Z2023-05-08T20:10:57ZPerfect perfume or eau de cat’s bum? Why scents smell different and 4 fragrance tips<figure><img src="https://images.theconversation.com/files/524549/original/file-20230505-19-gg63bb.jpg?ixlib=rb-1.1.0&rect=5%2C0%2C3489%2C2326&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><a class="source" href="https://www.pexels.com/photo/a-woman-spraying-perfume-8625562/">Pexels/Ron Lach</a></span></figcaption></figure><p>Mother’s Day is coming up in Australia and that means a surge in perfume sales. Of course, scents are purchased year-round and not just for mothers. Fragrance sales in Australia will amount to <a href="https://www.statista.com/outlook/cmo/beauty-personal-care/fragrances/australia%5D">over A$1 billion</a> this year.</p>
<p>The word “perfume” is derived from the Latin <em>per fumus</em>, meaning “through smoke”. The <a href="https://www.amazon.com/Mendeleyevs-Dream-Elements-Paul-Strathern/dp/0312262043">very first account</a> of using perfumes dates back to 1200 BC when a <a href="https://books.google.com.au/books/about/Women_of_Science.html?id=S7DaAAAAMAAJ&redir_esc=y">woman called Tapputi</a> mixed flowers, oils and various plants with water or solvents, then extracted their fragrance. The basis of this technique for making perfume is still used today. </p>
<p>But how do we smell? What makes perfume appealing? And why does it smell differently on different people?</p>
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<strong>
Read more:
<a href="https://theconversation.com/smell-like-a-woman-not-a-rose-chanel-no-5-100-years-on-an-iconic-fragrance-born-from-an-orphanage-158870">'Smell like a woman, not a rose': Chanel No. 5 100 years on, an iconic fragrance born from an orphanage</a>
</strong>
</em>
</p>
<hr>
<h2>The science of smell</h2>
<p>A sense of smell is vital to all species on Earth. One <a href="https://www.science.org/content/article/elephants-may-have-best-noses-earth">study</a> identified African elephants as having the “best noses” in the animal kingdom, not to mention the longest ones. It can help animals sniff out danger, food and mates. </p>
<p>For humans, too, being able to smell is not just for the enjoyment of pleasant odours. It can also protect us from toxic chemicals with noxious smells, such as <a href="https://www.cdc.gov/niosh/ershdb/emergencyresponsecard_29750038.html#:%7E:text=Hydrogen%20cyanide%20(AC)%20gas%20has,as%20a%20solution%20in%20water.">hydrogen cyanide</a>. </p>
<p>When something has an odour, it means it is chemically volatile – vaporising from a liquid to a gas. When we smell a scent, gas molecules enter our nose and stimulate specialised nerve cells called <a href="https://theconversation.com/curious-kids-how-do-we-smell-104772">olfactory sensory neurons</a>. When these neurons are triggered, they send a signal to the brain to identify the chemicals. </p>
<p>Humans have around 10 million of those neurons and around <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1905909/">400 scent receptors</a>. The human nose can distinguish at least <a href="https://www.science.org/content/article/human-nose-can-detect-trillion-smells#:%7E:text=These%20are%20only%20three%20of,never%20been%20explicitly%20tested%20before.">1 trillion different odours</a>, from freshly brewed coffee to wet dog to mouldy cheese.</p>
<p>The more volatile a compound is the lower its boiling point and, from a chemical perspective, the weaker the forces holding the molecules together. When this is the case, more molecules enter the gaseous state and the smell is more intense. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/524553/original/file-20230505-29-oq48q3.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="two women try perfumes" src="https://images.theconversation.com/files/524553/original/file-20230505-29-oq48q3.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/524553/original/file-20230505-29-oq48q3.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/524553/original/file-20230505-29-oq48q3.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/524553/original/file-20230505-29-oq48q3.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/524553/original/file-20230505-29-oq48q3.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/524553/original/file-20230505-29-oq48q3.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/524553/original/file-20230505-29-oq48q3.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Certain classes of chemical compounds smell better than others.</span>
<span class="attribution"><a class="source" href="https://www.pexels.com/photo/two-women-standing-beside-the-table-8275677/">Pexels/Ron Lach</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
</figcaption>
</figure>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/curious-kids-how-do-we-smell-104772">Curious Kids: How do we smell?</a>
</strong>
</em>
</p>
<hr>
<h2>What makes things smell good though?</h2>
<p>Different classes of chemical compounds can have more pleasant or offensive scents. </p>
<p>Fish and decaying animal cells, for example, release chemicals called <a href="https://chem.libretexts.org/Courses/BridgeValley_Community_and_Technical_College/Fundamentals_of_Chemistry/11%3A_Organic_Chemistry/11.15%3A_Amines#:%7E:text=Amines%20generally%20have%20rather%20pungent,odor%20associated%20with%20dead%20fish.">amines</a>, which don’t smell appealing. </p>
<p>Fruits, on the other hand, are composed of chemicals in a class of organic compounds called aldehydes, esters and ketones, which have sweeter and <a href="https://chem.libretexts.org/Courses/Sacramento_City_College/SCC%3A_CHEM_330_-_Adventures_in_Chemistry_(Alviar-Agnew)/09%3A_Organic_Chemistry/9.08%3A_Carboxylic_Acids_and_Esters#:%7E:text=Esters%20occur%20widely%20in%20nature,fragrances%20of%20fruits%20and%20flowers.">more pleasant odours</a>. </p>
<p>Chemists have been able to identify the <a href="https://jameskennedymonash.wordpress.com/2014/01/04/table-of-organic-compounds-and-their-smells-revised-edition/">specific chemical smells</a> released by substances we encounter in everyday life.</p>
<h2>Smells different</h2>
<p>So it makes sense that pleasant-smelling aldehydes, ketones and esters are used to create perfumes. However, some perfumes also contain unusual ingredients that don’t smell nice on their own. </p>
<p>For example, Chanel No. 5 perfume – the iconic 100-year-old favourite – contains civet as one of its base chemical notes. <a href="https://www.nytimes.com/1973/04/15/archives/a-boycott-of-chanel-no-5-urged-by-humane-groups.html">Civet</a> is used by perfumers for its <a href="https://theconversation.com/civet-musk-a-precious-perfume-ingredient-is-under-threat-steps-to-support-ethiopian-producers-and-protect-the-animals-193469">long-lasting, musky scent</a>. It is traditionally extracted from the anal glands of <a href="https://slate.com/technology/2012/07/chanel-no-5-a-brain-parasite-may-be-the-secret-to-the-famous-perfume.html">civet cats</a> but Chanel has used a synthetic form of civet <a href="https://www.ft.com/content/99a13235-cdb9-431b-b8f1-e52ce4a10486">since 1998</a>. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/524555/original/file-20230505-1846-tdgmp8.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="civet cat at night in the wild" src="https://images.theconversation.com/files/524555/original/file-20230505-1846-tdgmp8.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/524555/original/file-20230505-1846-tdgmp8.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/524555/original/file-20230505-1846-tdgmp8.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/524555/original/file-20230505-1846-tdgmp8.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/524555/original/file-20230505-1846-tdgmp8.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/524555/original/file-20230505-1846-tdgmp8.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/524555/original/file-20230505-1846-tdgmp8.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Today, perfumers can use synthetic civet in place of the real thing.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/close-african-civet-civettictis-civetta-night-1071600497">Shutterstock</a></span>
</figcaption>
</figure>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/civet-musk-a-precious-perfume-ingredient-is-under-threat-steps-to-support-ethiopian-producers-and-protect-the-animals-193469">Civet musk, a precious perfume ingredient, is under threat. Steps to support Ethiopian producers and protect the animals</a>
</strong>
</em>
</p>
<hr>
<h2>Tips for choosing and using perfumes</h2>
<p>Our ability to smell a perfume will depend on two factors: how well our olfactory sensory neurons are performing (a virus or infection could affect function, for example) and the volatility of the chemicals in the perfume. </p>
<p><strong>1. Try before you buy</strong></p>
<p>You can’t really do much about your sensory neurons, but you can increase the intensity of perfumes, such as by warming up the perfume on your skin or applying to pulse points. This will help to give molecules more energy and increase the number of molecules entering the gaseous state. </p>
<p>Specific perfumes will not smell the same on different people’s skin because the chemicals in them can be affected by the skin’s type and condition (dry or oily, acidic or base) and even their diet. Some foods we eat, such as garlic, are released from our bodies through our skin. Those chemicals can mask perfume chemicals. </p>
<p>So, it is better to buy someone their tried and true favourite scent rather than risking a new one. And those department store sample sprays can be useful to try before you buy. </p>
<p><strong>2. Moisturise before use</strong></p>
<p>When you spray perfume on very dry skin, some of the perfume’s chemicals – the large organic ones that are similar to skin’s natural oils – are absorbed by the skin and then into the sebaceous glands. When some notes in a perfume are absorbed this way, it can take on a different smell. That’s also why it’s better to moisturise skin before spraying perfume, so perfume chemicals stay on the skin for longer. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/524550/original/file-20230505-29-pyv9nv.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/524550/original/file-20230505-29-pyv9nv.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/524550/original/file-20230505-29-pyv9nv.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/524550/original/file-20230505-29-pyv9nv.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/524550/original/file-20230505-29-pyv9nv.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/524550/original/file-20230505-29-pyv9nv.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/524550/original/file-20230505-29-pyv9nv.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/524550/original/file-20230505-29-pyv9nv.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Try before you buy – scents smell different on different people.</span>
<span class="attribution"><a class="source" href="https://www.pexels.com/photo/man-in-blue-crew-neck-t-shirt-applying-perfume-8160475/">Pexels/Ron Lach</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
</figcaption>
</figure>
<p><strong>3. Experiment with spraying techniques</strong></p>
<p>To avoid changes in the scent of your favourite perfume and increase the time the perfume stays on you, you could spray your hair instead. Your hair is porous so perfume molecules might remain there longer. However, most perfumes contain alcohol, which dries out hair. Spraying perfume directly onto a hairbrush first, then brushing your hair, might prevent some of this drying effect. </p>
<p><a href="https://www.byrdie.com/how-to-apply-perfume">Spraying then walking</a> through a mist of perfume so the chemicals settle on your hair, skin and clothes might work – but you risk losing a lot of precious perfume with that technique.</p>
<p><strong>4. Keep it cool</strong></p>
<p>Temperature will <a href="https://www.researchgate.net/publication/5674095_Effect_of_Temperature_on_the_Floral_Scent_Emission_and_Endogenous_Volatile_Profile_of_Petunia_axillaris">affect volatility</a>. To keep perfumes lasting longer in the bottle, keep them in the fridge or cool dark place and tightly sealed to prevent your expensive, heat-sensitive scent evaporating into thin air.</p><img src="https://counter.theconversation.com/content/203905/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Magdalena Wajrak does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>From surprising ingredients to chemical compounds. Here’s why your favourite perfume might not smell so sweet on your mum.Magdalena Wajrak, Senior lecturer, Chemistry, Edith Cowan UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1889562023-03-13T12:26:33Z2023-03-13T12:26:33ZSmell is the crucial sense that holds ant society together, helping the insects recognize, communicate and cooperate with one another<figure><img src="https://images.theconversation.com/files/513805/original/file-20230306-20-apwc3a.jpg?ixlib=rb-1.1.0&rect=0%2C1224%2C2696%2C1582&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Ants from different colonies will fight based on smell alone.</span> <span class="attribution"><span class="source">Joseph Howell, Vanderbilt University</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span></figcaption></figure><p>Ants can be found in <a href="https://doi.org/10.1038/s41467-018-04218-4">nearly every location on Earth</a>, with rough estimates suggesting there are <a href="https://www.bbc.com/news/magazine-29281253">over 10 quadrillion individuals</a> – that is a 1 followed by 16 zeroes, or about 1 million ants per person. Ants are among the most biologically successful animals on the planet. </p>
<p>A surprising part of their evolutionary success is the amazing sense of smell that lets them recognize, communicate and cooperate with one another.</p>
<p>Ants live in complex colonies, sometimes referred to as nests, that are home to <a href="https://wwnorton.com/books/9780393067040">a wide range of social interactions</a>. Here, one or more queens are responsible for all the reproduction within that colony. The vast majority of colony members are female workers – sisters that never mate or reproduce and live only to serve the group.</p>
<p>Ants need to <a href="https://doi.org/10.1186/s12915-022-01505-x">defend their colony</a>, <a href="https://doi.org/10.1371/journal.pone.0052219">seek food</a> and <a href="https://doi.org/10.1086/690840">take care of offspring</a>. To accomplish these tasks some ant species domesticate other insects, while others create agricultural systems, harvesting leaves from which they <a href="https://doi.org/10.1086/661128">grow edible fungal gardens</a>. Successfully coordinating all these intricate tasks requires reliable and secure communication among nestmates.</p>
<p><a href="https://scholar.google.com/citations?user=PrNrnI8AAAAJ&hl=en&oi=sra">We</a> <a href="https://scholar.google.com/citations?hl=en&user=IZUwOQ0AAAAJ">are</a> biologists who study the remarkable sensory abilities of ants. <a href="https://lab.vanderbilt.edu/zwiebel-lab/">Our recent work</a> shows how their societies depend on the exchange of reliable information which, if disrupted, spells doom for their colonies.</p>
<h2>Unique scents</h2>
<p>Human communication relies primarily on verbal and visual cues. We usually identify our friends by the sound of their voice, the appearance of their face or the clothes they wear. Ants, however, <a href="https://doi.org/10.1242/jeb.215400">rely primarily on their acute sense of smell</a>. </p>
<p>An exterior shell, known as an exoskeleton, encases an ant’s body. This greasy coat carries a unique scent that varies from individual to individual and gives each ant a <a href="https://www.hup.harvard.edu/catalog.php?isbn=9780674040755">unique odor signature that other ants can detect</a>. This odor signature can communicate important information. </p>
<p>The queen, for example, will smell slightly different from a worker, and thus receive special treatment within the colony. Importantly, ants from different colonies will smell slightly different from one another. The detection and decoding of these differences is <a href="https://doi.org/10.3389/fnbeh.2018.00191">vital for colony defense</a> and can trigger aggressive turf wars between colonies when ants catch a whiff of intruders.</p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/-ZFWVCkBcxI?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">Interactions between nestmates are friendly. But when ants sniff out enemy non-nestmates, there is rapid and deadly aggression. Produced by the Zwiebel Lab, Vanderbilt University, filmed by Stephen Ferguson.</span></figcaption>
</figure>
<p>For ants and other insects, receiving chemical information begins when an odor enters the small hairs located along their antennae. These hairs are hollow and contain <a href="https://doi.org/10.1016/j.cois.2014.10.006">special receptors, called chemosensory neurons</a>, that sort and send the chemical information to the ant’s brain. </p>
<p>Odors, such as those given off from an ant’s greasy coat, <a href="https://doi.org/10.1242/jeb.215400">act like chemical “keys</a>.” Ants can smell these odor keys only if they are inserted into the correct set of chemosensory neuron “locks.” A neuronal lock remains shut to any odors except its particular key. When the correct key binds to the correct neuronal lock, though, the receptor sends a complex message to the brain. The ant’s brain is able to decode this sensory information to make decisions that ultimately lead to cooperation between nestmates – or battles between non-nestmates. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/514327/original/file-20230308-22-8r9eol.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A Tupperware container filled with ants. Three test tubes with cotton stoppers appear to hold water." src="https://images.theconversation.com/files/514327/original/file-20230308-22-8r9eol.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/514327/original/file-20230308-22-8r9eol.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/514327/original/file-20230308-22-8r9eol.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/514327/original/file-20230308-22-8r9eol.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/514327/original/file-20230308-22-8r9eol.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/514327/original/file-20230308-22-8r9eol.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/514327/original/file-20230308-22-8r9eol.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=566&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">A colony of carpenter ants (<em>Camponotus floridanus</em>) reared in the Zwiebel Lab at Vanderbilt University.</span>
<span class="attribution"><span class="source">LJ Zwiebel, Vanderbilt University</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<h2>Changing the locks</h2>
<p>To better understand how ants detect and communicate information, we use laboratory tools such as <a href="https://doi.org/10.1242/jeb.215400">precisely targeted drugs</a> and <a href="https://doi.org/10.1016/j.cell.2017.06.051">genetic</a> <a href="https://doi.org/10.1016/j.cell.2017.07.001">engineering</a> to manipulate their sense of smell. We are especially interested in what happens when an ant’s sense of smell goes wrong. </p>
<p>For example, when we prevent an odor “key” from opening a chemosensory “lock,” it prevents the chemical information from reaching the brain. This would be like plugging your nose or standing in a completely dark room – no scents or sights would register. We can also open all the “locks” at the same time, which floods the neurons with too many messages. Both of these scenarios dramatically compromise an ant’s ability to detect and receive accurate information.</p>
<p>When we messed with ants’ sense of smell – whether shutting down or flooding their odor receptors – we found <a href="https://doi.org/10.1242/jeb.215400">they no longer attacked non-nestmates</a>. Instead, they became less aggressive. In the absence of clear information, ants exercised restraint and opted to accept rather than attack their fellow ant. Put another way, ants ask questions first and shoot later. </p>
<p>We believe this social restraint is hard-wired and gives ants an evolutionary advantage. When you live in a colony with tens of thousands of sisters, a simple case of mistaken identity or miscommunication could lead to deadly infighting and societal chaos, which is potentially very costly.</p>
<p>When ants in our experiments lose their sense of smell, and their ability to detect accurate information becomes compromised, <a href="https://doi.org/10.1016/j.cell.2017.06.051">they no longer stick together</a> <a href="https://doi.org/10.1016/j.cell.2017.07.001">in a cohesive colony</a>. </p>
<p>Not only do they fail to recognize and attack foes, they also stop cooperating with their friends. Without nurses to take care of the young or foragers to collect food, the eggs dry up and the queen goes hungry. </p>
<p>We discovered that without an accurate means of communicating and receiving chemical information, ant societies collapse and the colony quickly dies. Miscommunication or the lack of accurate information <a href="https://www.pbs.org/newshour/nation/miscommunication-blamed-deadly-u-s-mistake-afghanistan">affects other highly social animals, including humans</a>, as well. For ants, it all depends on their sense of smell.</p><img src="https://counter.theconversation.com/content/188956/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Laurence Zwiebel currently receives funding from the NIH and Vanderbilt University. </span></em></p><p class="fine-print"><em><span>Stephen Ferguson currently receives funding from the NIH and Vanderbilt University.</span></em></p>Researchers explore what happens when ants can’t properly use smell to detect friend from foe.Laurence Zwiebel, Professor of Biological Sciences and of Pharmacology, Vanderbilt UniversityStephen Ferguson, Postdoctoral Scholar in Biological Sciences, Vanderbilt UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1931792022-12-08T19:25:39Z2022-12-08T19:25:39Z5 senses? In fact, architects say there are 7 ways we perceive our environments<figure><img src="https://images.theconversation.com/files/499825/original/file-20221208-14230-eo32y0.jpg?ixlib=rb-1.1.0&rect=134%2C291%2C1413%2C855&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Spa bath in a complex designed by architect Peter Zumthor over thermal springs in the Vals Valley, Switzerland. </span> <span class="attribution"><a class="source" href="https://creativecommons.org/licenses/by-nc/2.0/">(Mariano Mantel/Flickr)</a>, <a class="license" href="http://creativecommons.org/licenses/by-nc/4.0/">CC BY-NC</a></span></figcaption></figure><iframe style="width: 100%; height: 100px; border: none; position: relative; z-index: 1;" allowtransparency="" allow="clipboard-read; clipboard-write" src="https://narrations.ad-auris.com/widget/the-conversation-canada/5-senses-in-fact--architects-say-there-are-7-ways-we-perceive-our-environments" width="100%" height="400"></iframe>
<p>Have you ever wondered why you feel cozy in some places while you feel stunned in others? Think about the last international airport you landed in, or a local coffee shop in your neighbourhood. </p>
<p>How we perceive these places is multifaceted. We often hear that we perceive our environments <a href="https://www.theweeklyjournal.com/business/using-the-five-senses-in-marketing-is-a-must/article_112c8b0e-71a0-11ed-967e-17935054a27f.html">through five senses</a>: sight, smell, touch, sound and taste. But what if there are more senses involved in our perception? </p>
<p>Architects concerned with “the ways we experience things, thus the meanings things have in our experience,” as articulated in the branch of <a href="https://plato.stanford.edu/entries/phenomenology">philosophy known as phenomenology</a> are <a href="https://stoutbooks.com/products/questions-of-perception-phenomenology-of-architecture-1">concerned with a fuller picture of how we perceive our environments</a>.</p>
<h2>More senses</h2>
<p>Beyond the traditional five senses, neuroscientific research also <a href="https://www.sciencedirect.com/topics/neuroscience/proprioception">examines proprioception</a> (sensing your muscles, their location, and their movements) and <a href="https://www.sciencedirect.com/topics/neuroscience/vestibular-system">the vestibular system,</a> which regulates the sense of orientation and balance in space.</p>
<p>Scientists are also examining <a href="https://www.theguardian.com/science/2021/aug/15/the-hidden-sense-shaping-your-wellbeing-interoception">a sense called “interoception” </a> which refers to the perception of sensation from inside
your body. The most commonly experienced one is having butterflies.</p>
<figure class="align-center ">
<img alt="A thin structure appears to be on wooden stilts nestled against sheer rock." src="https://images.theconversation.com/files/499566/original/file-20221207-10117-78sqem.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/499566/original/file-20221207-10117-78sqem.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=452&fit=crop&dpr=1 600w, https://images.theconversation.com/files/499566/original/file-20221207-10117-78sqem.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=452&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/499566/original/file-20221207-10117-78sqem.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=452&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/499566/original/file-20221207-10117-78sqem.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=567&fit=crop&dpr=1 754w, https://images.theconversation.com/files/499566/original/file-20221207-10117-78sqem.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=567&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/499566/original/file-20221207-10117-78sqem.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=567&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Allmannajuvet Zinc Mine Museum in Sauda, southern Norway, designed by Peter Zumthor.</span>
<span class="attribution"><span class="source">(Astrid Westvang/Flickr)</span>, <a class="license" href="http://creativecommons.org/licenses/by-nc-nd/4.0/">CC BY-NC-ND</a></span>
</figcaption>
</figure>
<h2>Phenomenology in architecture</h2>
<p>While architects across cultures and time have long considered the senses and design, the concerns of phenomenology as articulated by philosopher Martin Heidegger were introduced into architecture through <a href="https://doi.org/10.1080/13264821003629279">architect Christian Norberg-Schulz</a> beginning in the early ‘70s.</p>
<p>Architects concerned with phenomenology are interested in how to integrate a renewed fundamental <a href="https://books.google.ca/books/about/Questions_of_Perception.html?id=r7gyAQAAIAAJ&redir_esc=y">understanding of perception</a> to design better buildings. </p>
<p>Phenomenology in architecture refers to a shifting focus on giving users an experience. Beyond <a href="https://books.google.ca/books/about/Genius_Loci.html?id=FlYkAQAAMAAJ&redir_esc=y">Norberg-Schulz</a>, architects <a href="https://doi.org/10.1177/1357034X16676540">Juhani Pallasmaa</a> and <a href="https://www.oasejournal.nl/en/Issues/58/PhenomenologyAndVirtualSpace#035">Alberto Pérez-Gómez</a> have developed this approach, and architects Steven Holl and Peter Zumthor design based on the theories. </p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/NqlyDCXY9p0?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">Video about phenomenology in architecture.</span></figcaption>
</figure>
<h2>Thinking about approaching</h2>
<p>Our <a href="https://books.google.ca/books/about/The_Concept_of_Dwelling.html?id=4xxQAAAAMAAJ&redir_esc=y">perception of approaching</a> a building, a city or an object within an environment depends on many factors.</p>
<p>Approaching a city in the middle of the desert is entirely different than approaching a town in a forest. </p>
<p>You can perceive and see a city in a desert in plain sight, and you might perceive the duration it takes to get there longer than it is in reality. When approaching a town in a forest, you will be busy looking around the forest, looking at animals or trees, and experiencing a shorter time than what it took you to get there. </p>
<p>When it comes to buildings, you will first approach them, enter them, and finally start exploring them. From the moment you are on the path of approaching, you start perceiving <a href="https://www.sciencedirect.com/referencework/9780128054093/the-senses-a-comprehensive-reference">with all your different senses</a>. </p>
<figure class="align-center ">
<img alt="A wooden walkway seen extending through water and greenery leading towards a building complex." src="https://images.theconversation.com/files/499565/original/file-20221207-12015-yvtyxk.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/499565/original/file-20221207-12015-yvtyxk.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/499565/original/file-20221207-12015-yvtyxk.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/499565/original/file-20221207-12015-yvtyxk.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/499565/original/file-20221207-12015-yvtyxk.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/499565/original/file-20221207-12015-yvtyxk.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/499565/original/file-20221207-12015-yvtyxk.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Part of the Linked Hybrid complex in Beijing, designed by Steven Holl Architects.</span>
<span class="attribution"><span class="source">(Wojtek Gurak/Flickr)</span>, <a class="license" href="http://creativecommons.org/licenses/by-nc/4.0/">CC BY-NC</a></span>
</figcaption>
</figure>
<p>Here are some tangible examples:</p>
<p><strong>Touch:</strong> Imagine the moment you are going to touch a front door knob. A wooden door knob will feel different than a steel one.</p>
<p><strong>Smell:</strong> Sometimes, a specific smell can remind you of beautiful memories. It’s the same when it comes to buildings. Everyone can differentiate between the scent of a clean vacant space and a cottage in the woods.</p>
<p><strong>Sound:</strong> You can get different feelings of space by just perceiving it with your ears. Compare a room with ceramic tiles where you hear shoes clacking along the floor and walking on a wooden floor where you hear the wooden floors. </p>
<figure class="align-right ">
<img alt="Image of a house in the distance with a light on in the darkness and snow falling around it." src="https://images.theconversation.com/files/499814/original/file-20221208-14351-65pkn0.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/499814/original/file-20221208-14351-65pkn0.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=396&fit=crop&dpr=1 600w, https://images.theconversation.com/files/499814/original/file-20221208-14351-65pkn0.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=396&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/499814/original/file-20221208-14351-65pkn0.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=396&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/499814/original/file-20221208-14351-65pkn0.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=498&fit=crop&dpr=1 754w, https://images.theconversation.com/files/499814/original/file-20221208-14351-65pkn0.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=498&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/499814/original/file-20221208-14351-65pkn0.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=498&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Do you see, hear or smell a fire?</span>
<span class="attribution"><span class="source">(Shutterstock)</span></span>
</figcaption>
</figure>
<p><strong>Sight:</strong> All of us have seen pictures showing a small house in the distance where a small light is on on a snowy day. That tiny light on a snowy day can be a fireplace we can feel just by seeing it in the distance.</p>
<p><strong>Taste:</strong> It might be hard to link taste to architecture, but architecture can be a stimulus for taste. Specific colours and details can stimulate taste. For instance, marble might give you <a href="https://www.theguardian.com/lifeandstyle/wordofmouth/2013/mar/12/how-taste-different-colours">a particular sensation of taste</a>.</p>
<p><strong>Vestibular (movement) and proprioception (body position):</strong> These two senses are the foundation for orienting yourself in a space and being self-conscious within an environment.</p>
<h2>Stimuli in our environments</h2>
<p>It’s important to also consider what <a href="https://www.stevenholl.com/">Steven Holl</a>, a New York-based architect, believes <a href="https://books.google.ca/books/about/Questions_of_Perception.html?id=r7gyAQAAIAAJ&redir_esc=y">are the 11 stimuli in our environments that affect our perception</a>.</p>
<p>1) An object is perceived within its surrounding. If you have a flower in front of your windows, the background will also play an important role in perceiving it and your impression of the flower. </p>
<p>2) Our perception is a series of frames from our environment that changes with our every single move.</p>
<p>3) <a href="https://books.google.bg/books/about/Colors.html?id=RRklvgAACAAJ&redir_esc=y">Colours</a> have an important role in our perception. </p>
<p>4) Light and shadows can give us different feelings.</p>
<p>5) Night and day can yield completely different experiences.</p>
<figure class="align-center ">
<img alt="A white rectangular building seen reflected into water beside it." src="https://images.theconversation.com/files/499564/original/file-20221207-26-xuglf3.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/499564/original/file-20221207-26-xuglf3.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=379&fit=crop&dpr=1 600w, https://images.theconversation.com/files/499564/original/file-20221207-26-xuglf3.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=379&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/499564/original/file-20221207-26-xuglf3.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=379&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/499564/original/file-20221207-26-xuglf3.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=476&fit=crop&dpr=1 754w, https://images.theconversation.com/files/499564/original/file-20221207-26-xuglf3.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=476&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/499564/original/file-20221207-26-xuglf3.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=476&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Nelson-Atkins Museum of Art, Kansas City, Mo., designed by Steven Holl Architects.</span>
<span class="attribution"><span class="source">(Dean Hochman/Flickr)</span>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
</figcaption>
</figure>
<p>6) Perception of time is not linear and depends on many different factors.</p>
<p>7) Water is a reflection of its surrounding environment.</p>
<p>8) Sound helps to perceive our environment. Imagine measuring the depth of a room by echoing.</p>
<p>9) Details in design are an essential factor that can have different impacts. A person can easily differentiate the feeling and taste of natural wood from an artificial one.</p>
<p>10) <a href="https://www.routledge.com/Proportion-Science-Philosophy-Architecture/Padovan/p/book/9780419227809">Proportions and scales</a> are other critical factors in perceiving our environment. If a building is too big in scale, it can give you a feeling of being stunned, while a lower ceiling height can make you feel cozy.</p>
<p>11) Ideas are vital in designing buildings as they can give people different experiences.</p>
<p>Accordingly, if you want to create a cozy coffee shop, you design it with low lights, warm colors, a nice ambient sound. An idea at the centre influences details with furniture and interiors, ceiling height and everything else.</p>
<p>Phenomenology in architecture helps create better environments based on how humans perceive their surroundings. Whether you are planning to go to a local restaurant or an exhibition, you can now think about how your experiences in a space are related to your sense perception.</p><img src="https://counter.theconversation.com/content/193179/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Farzam Sepanta does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>Stimuli such as light and shadow and our perception of the passage of time matter to architects interested in the branch of philosophy known as phenomenology.Farzam Sepanta, PhD Candidate, Building Engineering, Carleton UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1920632022-10-20T16:06:01Z2022-10-20T16:06:01ZThree reasons strong perfumes give you a headache<figure><img src="https://images.theconversation.com/files/490078/original/file-20221017-16-mo7d9w.jpg?ixlib=rb-1.1.0&rect=0%2C0%2C7856%2C5304&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Many people find the smell of strong perfumes to be irritating.</span> <span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/perfume-bottles-transparent-multicolored-glass-cosmetics-2001950825">GVLR/ Shutterstock</a></span></figcaption></figure><p>Humans can smell <a href="https://www.nature.com/articles/nature.2014.14904">over 1 trillion odours</a>. But no two people will react in quite the same way to the same smell. While there are some smells almost everyone agrees are unpleasant (such as paint thinner or rotten food), our reactions to other types of smells can be far more personal. </p>
<p>Take perfume. While one person may find the smell of a strong, floral perfume to be heavenly, another person may find it gives them a headache. There are many reasons why people can get a physical reaction to strong smells – but here are the three most common ones.</p>
<h2>1. Emotions</h2>
<p>Of all of our senses, only smell has a direct line to <a href="https://link.springer.com/chapter/10.1007/978-1-4612-2836-3_15">our emotional system</a>. It’s thought the reason for this link is because smell evolved first of all of our senses. This means we don’t just perceive smell based on the odour chemicals presented to us, but together with all <a href="https://doi.org/10.3758/BF03210754">our memories of that smell</a> – including the way it makes us feel, our past memories, and how we presently feel.</p>
<p>So let’s say you smell something you associate with a negative memory. Perhaps it’s the smell of cleaning chemicals used in a hospital, or the same perfume your ex used. One whiff may cause <a href="https://www.frontiersin.org/articles/10.3389/fnsys.2021.752320/full">all those negative emotions</a> to come rushing back to you, leading your body to <a href="https://www.jneurosci.org/content/33/39/15324.short">generate a fight or flight stress response</a>. </p>
<p>The fight or flight stress response is your body’s way of reacting to stress, anxiety or danger. It causes a number of physical changes, most of which are triggered by the brain going into high alert. One of the first changes you may notice during a fight or flight response is tension around the head and neck area. The reason for this is due to a vasodilation (widening of the blood vessels) which allows more blood to be diverted to the brain and parts of the body that need it.</p>
<p>Vasodilation also activates sensory receptors embedded in the blood vessels, which <a href="https://www.bloomsbury.com/uk/splitting-9781472971395/">we perceive as headache</a> pain if the blood vessels in the head and neck are the ones widening.</p>
<p>How we respond emotionally to certain smells is very personal, and based on a <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC20578/">myriad of experiences</a>. It may even be triggered by smells we may not even be conscious of smelling or consciously aware of our reaction to them. But if you tend to get headaches only when you smell certain scents, it may be due to the negative association you have to it.</p>
<h2>2. Sinus troubles</h2>
<p>The chemicals that activate the smell signals in our brain (called odorants) can sometimes irritate our sinuses. Smoke, perfume and chlorine are some of the most common odorants that cause irritation. </p>
<p>Our sinuses comprise of four distinct, air-filled cavities in the bones of our face. Each are lined with a mucus-secreting membrane. The mucus traps particles and bugs that come in through our nose and mouth. But in order to clear these trapped particles or potential irritants, the body needs to produce more and more mucus – resulting in allergy-like symptoms. This in turn causes our immune system to kick in and help out, which results in vasodilation and inflammation. The <a href="https://www.bloomsbury.com/uk/splitting-9781472971395/">end result for some is a headache</a>.</p>
<figure class="align-center ">
<img alt="A man presses his hands to his temples, his eyes shut in pain from his headache." src="https://images.theconversation.com/files/490076/original/file-20221017-16-l7skur.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/490076/original/file-20221017-16-l7skur.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/490076/original/file-20221017-16-l7skur.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/490076/original/file-20221017-16-l7skur.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/490076/original/file-20221017-16-l7skur.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/490076/original/file-20221017-16-l7skur.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/490076/original/file-20221017-16-l7skur.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Many odorants can cause allergy-like symptoms that lead to a headache.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/displeased-handsome-guy-headache-rubbing-his-1933229045">Dean Drobot/ Shutterstock</a></span>
</figcaption>
</figure>
<p>Some odours may also <a href="https://doi.org/10.1021/cn100102c">act directly on the nerve pathway</a> that transmits the sensory signals to the brain, too. Called the trigeminal pathway, this scoops up all the sensory signals from our head and carries them through the nerve cells to the brain for processing. </p>
<p>When this pathway is stimulated it causes inflammation because it detects a threat that only the immune system can sort out. This, too, can lead to a headache. Chemical smells such as formaldehyde, certain cleaning products and cigarette smoke are all known to act directly on the trigeminal pathway. </p>
<h2>3. Odour intolerance</h2>
<p>Osmophobia is defined as an intolerance to odours. While rare on its own, people who suffer from chronic headaches tend to also experience osmophobia.</p>
<p>Migraine sufferers are <a href="https://americanheadachesociety.org/news/whats-that-smell/#:%7E:text=Osmophobia%252C%2520a%2520sensitivity%2520to%2520smell,some%2520cleaning%2520products%2520and%2520foods.">particularly prone to osmophobia</a>. Some research has even shown that exposure to strong odours for two hours or more can actually trigger a migraine in <a href="https://journals.sagepub.com/doi/10.1177/0333102416636098#:%7E:text=In%2520our%2520study%252C%252034.7%2525%2520of,to%252070.0%2525%2520of%2520these%2520patients.">around 20% of migraine sufferers</a>. Cigarette smoke, perfumes, car exhaust and cleaning products are some of the most common triggering scents.</p>
<p>The nervous system of someone who experiences migraine can be particularly sensitive to certain sensory stimuli in their daily life. But during the prodrome phase (the first of four distinct migraine phases, which may happen a couple of days to hours before the headache attack) they may become <a href="https://www.bloomsbury.com/uk/splitting-9781472971395/">even more sensitive to certain stimuli</a> – including smells.</p>
<p>Many migraine sufferers experience certain signs that a migraine is coming during the podrome phase – such a yawning more and craving certain foods. Smells that wouldn’t ordinarily bother you may also <a href="https://doi.org/10.1007/BF00313864">upset you intensely</a>. You may also perceive smells that aren’t there – known as <a href="http://cep.sagepub.com/content/31/14/1477.full.pdf+html">phantom smells</a>. The most common phantom smell many report before a migraine is a burning smell. So while smell isn’t the migraine trigger in this instance, it may be a sign of an oncoming headache.</p>
<p>Science has yet to find an effective way to get around this. So, if you’re someone that tends to get headaches from certain scents (no matter the reason) perhaps it’s best to avoid them as much as you can. But since we can’t always avoid triggers, fresh air and painkillers may be the best way to manage any headaches that do occur.</p><img src="https://counter.theconversation.com/content/192063/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Amanda Ellison does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>No two people will react to the same smell in the same way.Amanda Ellison, Professor of Neuroscience, Durham UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1912122022-09-28T18:03:23Z2022-09-28T18:03:23ZDogs can smell people’s stress – new study<figure><img src="https://images.theconversation.com/files/487139/original/file-20220928-20-u0zwwd.png?ixlib=rb-1.1.0&rect=90%2C8%2C2775%2C1499&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><span class="source">Matt Donnelly </span>, <span class="license">Author provided</span></span></figcaption></figure><p>Dogs have a long history alongside humans, giving them an amazing ability to read human cues. Dogs also possess an incredible sense of smell, which enables them to detect diseases, <a href="https://link.springer.com/article/10.1186/s12879-021-05939-6">such as COVID</a> and <a href="https://iopscience.iop.org/article/10.1088/1752-7163/ab716e/meta">lung cancer</a>, in humans from odour alone. Whether dogs’ capabilities extend to detecting odours associated with psychological states has been explored far less. </p>
<p>When people are stressed, there are hormonal and nervous system changes that alter the kinds of odours produced by the body. My colleagues and I wanted to know if dogs can discriminate between odour samples taken from the same person before and after becoming stressed. To do this, we took ideas from the field of biomedical detection dogs (sniffer dogs in a laboratory setting) and combined these ideas with techniques used to test dogs’ perceptions of odours.</p>
<p>Our results are published in the journal <a href="https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0274143">PLOS One</a>.</p>
<p>To test whether dogs could detect an odour associated with psychological stress, we attached sensors to the study participants to continuously measure their heart rate and blood pressure. Participants also rated how stressed they were feeling before and after taking part in the task. </p>
<p>Before the task started, participants wiped gauze on the back of their neck, placed it into a sterile glass vial, and exhaled into the vial. We then got the participants to perform a rapid mental arithmetic task to induce stress in them. </p>
<p>After the task, participants provided another rating of their stress and two additional sweat/breath samples. </p>
<p>The total time between the collection of the relaxed (pre-task) and stressed (post-task) samples was four minutes, reducing the likelihood that the participants experienced changes other than the onset of stress. </p>
<p>We only included samples in the study if the person reported finding the task stressful, and both their heart rate and blood pressure had increased during the task. We presented samples from 36 people to the dogs. </p>
<h2>The training process</h2>
<p>The dogs included in this study were pets, volunteered by their owners, who were trained using positive reinforcement by researchers in a laboratory once a week. Before formal data collection began, dogs were taught to communicate that they were picking a sample by standing and freezing above it for several seconds or sitting in front of it – we called this their “alert behaviour”.</p>
<p>The dogs were then taught a matching game, where they learned to discriminate between samples with known odour differences. Once it was established that the dogs were successful at this, they were ready to be tested. </p>
<p>At testing, we tasked the dogs with discriminating between a person’s samples taken before and after the arithmetic task. To teach the dogs what odour they should be looking for in each testing session, they were first shown the person’s stress sweat/breath sample alongside two “control samples” – clean gauze in glass vials with no sweat or breath. </p>
<p>The dogs were allowed to sniff all three samples and were rewarded for alerting the researchers to the sweat/breath sample. </p>
<p>After ten exposures, a second breath/sweat sample was added to the line-up: the same person’s relaxed sample. Here began the test of discrimination, which took place over the next 20 trials. It was the dogs’ job to communicate, through their alert behaviour, which sample they perceived as the same as the one shown to them in the previous ten trials, that is, which sample smelled like the stress sample. Because dogs might use other information to help them make a choice, we included both visual and odour controls. </p>
<p>If these two odours smell the same to the dog, we would expect them to pick either by chance. If the two odours smell different, they would be able to consistently find the odour first presented to them: the stress odour. Each sample set from participants was used only once, so the dogs saw samples from a different person during each session. </p>
<p>From the very first time the dogs were exposed to these samples, they perceived the samples as smelling different. The dogs correctly chose the stress sample in 94% of 720 trials, showing that the participants’ psychological experience of the arithmetic task had resulted in their body emitting odours in their breath and sweat that the dogs could detect. </p>
<p>It should be noted that this study does not determine whether the dogs perceived the stress samples as reflecting a negative emotional state. It is likely that in a real-life setting dogs use a variety of contextual cues, such as our body language, tone of voice, or breathing rate, to help them understand a situation. However, the results provide firm evidence that odour is also a component that dogs can pick up on. </p>
<p>Establishing that dogs can detect an odour associated with human stress provides deeper knowledge of the human-dog relationship and adds to our understanding of how dogs perceive and interact with human psychological states. This knowledge could also be useful for the training of anxiety and PTSD service dogs that are currently trained to respond predominantly to visual cues.</p><img src="https://counter.theconversation.com/content/191212/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Clara Wilson does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>New research finds that psychological stress has an odour - and dogs can smell it.Clara Wilson, PhD Candidate, Psychology, Queen's University BelfastLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1845612022-08-17T04:09:20Z2022-08-17T04:09:20ZWhy do my feet smell? And what can I do about it?<figure><img src="https://images.theconversation.com/files/479559/original/file-20220817-20-7olb0l.jpg?ixlib=rb-1.1.0&rect=0%2C0%2C1000%2C666&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><span class="source">Shutterstock</span></span></figcaption></figure><p>“Smelly” might be the first word that comes to mind when you think of feet.</p>
<p>Why do some people’s feet have no smell, yet other feet are so pungent they could almost <a href="https://youtu.be/jAT4zNSB838">knock you out</a>? </p>
<p>Let’s go through what causes smelly feet, what you can do about it, and when to seek professional advice.</p>
<h2>Sweaty feet</h2>
<p>Sweaty feet can lead to smelly feet.</p>
<p>Feet can become sweaty in hot weather, especially if we wear a closed-in shoe or boot and the sweat doesn’t evaporate.</p>
<p>Anxiety and emotional stress also increase the <a href="https://psychcentral.com/anxiety/anxiety-sweat#link">activity</a> of sweat glands due to the release of stress hormones such as adrenaline, causing sweaty hands and feet. </p>
<p>Sweaty feet are common, but some people have an excessive sweating condition called “<a href="https://www.racgp.org.au/afp/2013/may/hyperhidrosis-and-bromhidrosis">hyperhidrosis</a>”. It’s very distressing and can lead to social awkwardness, reduced self-confidence and poor mental health. </p>
<p>But sweat usually doesn’t have a smell by itself. It’s the bacteria that feast on sweat that cause the bad smell.</p>
<h2>Bacteria and sweat</h2>
<p>Humans have around 1,000 species of <a href="https://health.howstuffworks.com/wellness/men/sweating-odor/bacteria-cause-body-odor.htm">bacteria</a> living on our skin. Bacteria thrive in moist environments such as our armpits, groin and also in between our toes. The bacteria living on our skin are mostly harmless (and some are even good for us), but they can also cause odour when they interact with sweat.</p>
<p><a href="https://pubmed.ncbi.nlm.nih.gov/16699586/">Foot odour</a> is associated with several types of bacteria. When these bacteria eat the sugars and fats in sweat, they produce chemicals with a <a href="https://www.bing.com/videos/search?q=why+does+my+body+smell+you+tube&view=detail&mid=A840EA2AFFA0616EB2F5A840EA2AFFA0616EB2F5&FORM=VIRE">noxious smell</a>. </p>
<p>The most common chemical compounds are:</p>
<ul>
<li><p>“isovaleric acid”, which has a distinctive cheesy, sweaty feet <a href="https://www.discovermagazine.com/planet-earth/bacteria-give-feet-4-distinct-odors">odour</a></p></li>
<li><p>“propionic acid”, which <a href="https://www.healthline.com/health/feet-smell-like-vinegar#:%7E:text=Foot%20sweat%20on%20some%20people,odor%20that%20smells%20like%20vinegar.">smells sour</a>. </p></li>
</ul>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/why-do-my-armpits-smell-and-would-using-glycolic-acid-on-them-really-work-183354">Why do my armpits smell? And would using glycolic acid on them really work?</a>
</strong>
</em>
</p>
<hr>
<p>A type of bacteria called “<a href="https://thecheesewanker.com/cheese-science/why-some-cheeses-smell-like-feet/#:%7E:text=Brevibacterium%20linens%3A%20The%20bacteria%20behind%20it%20all%20The,a%20harmless%20bacterium%20that%20lives%20on%20our%20skin.">brevibacteria</a>” also cause foot odour. They eat dead skin on our feet, producing a gas which has a distinctive sour smell.</p>
<p><a href="https://thecheesewanker.com/cheese-science/why-some-cheeses-smell-like-feet/#:%7E:text=Brevibacterium%20linens%3A%20The%20bacteria%20behind%20it%20all%20The,a%20harmless%20bacterium%20that%20lives%20on%20our%20skin.">Cheesemakers</a> will often add this bacteria to the surface of cheese to develop texture and flavour. This explains why many cheeses smell like feet, and feet smell like cheese!</p>
<p>Biologist Bart Knols received an “Ig Nobel” Prize (for unusual scientific achivements) in 2006 for demonstrating that a type of mosquito known for transmitting malaria has an equal preference for <a href="https://www.thelancet.com/journals/lancet/article/PIIS0140-6736(05)65812-6/fulltext">Limburger cheese</a> and the smell of human feet.</p>
<figure class="align-center ">
<img alt="Woman smells man's smelly feet" src="https://images.theconversation.com/files/479087/original/file-20220815-20-73f28m.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/479087/original/file-20220815-20-73f28m.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/479087/original/file-20220815-20-73f28m.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/479087/original/file-20220815-20-73f28m.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/479087/original/file-20220815-20-73f28m.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/479087/original/file-20220815-20-73f28m.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/479087/original/file-20220815-20-73f28m.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">There’s a reason feet sometimes smell like cheese.</span>
<span class="attribution"><span class="source">Shutterstock</span></span>
</figcaption>
</figure>
<h2>What else can cause smelly feet?</h2>
<p>Foot odour is made worse by socks and shoes that don’t allow sweat to evaporate from the skin. When sweat can’t evaporate from the skin, the temperature and relative humidity rise inside footwear, particularly in shoes such as <a href="https://www.researchgate.net/publication/303487588_THE_MICROCLIMATE_IN_PROTECTIVE_FIRE_FIGHTER_FOOTWEAR_FOOT_TEMPERATURE_AND_AIR_TEMPERATURE_AND_RELATIVE_HUMIDITY">work boots</a>.
Bacteria prefer a warm, damp environment.</p>
<p>A bacterial skin infection called “<a href="https://dermnetnz.org/topics/pitted-keratolysis">pitted keratolysis</a>” may also cause bad foot odour. It typically affects the soles of the feet and in between toes, and makes the skin white and soggy, often with clusters of small punched-out craters or “pits”. These pits are caused by bacteria digesting the skin and producing sulphur compounds. </p>
<p>It’s more common in men than women and is associated with sweaty feet, poor foot hygiene, diabetes and <a href="https://dermnetnz.org/topics/immunodeficiency">immunodeficiency</a>. Pitted keratolysis will respond to <a href="https://dermnetnz.org/topics/pitted-keratolysis">treatment</a> with antiseptic agents and topical antibiotics.</p>
<p>Foot odour can also be caused by tinea, a fungal skin infection often called athlete’s foot, which a podiatrist will be able to diagnose. It can be treated with an anti-fungal cream or lotion. </p>
<h2>What you can do to manage sweaty and smelly feet</h2>
<p>The first things to consider if you have smelly feet are foot hygiene and footwear. </p>
<p>Feet don’t wash themselves in the shower. In fact, bacteria from the rest of your body are washed down to your feet. So, it’s important to wash your feet with soap – including between your toes!</p>
<p>Drying your feet thoroughly after bathing is also important to prevent the build-up of sweat and bacteria.</p>
<p>It’s ideal to alternate your footwear so that shoes and boots have a chance to dry out before you wear them again. Damp footwear is the perfect place for bacteria to thrive and create those smelly chemicals.</p>
<p>Regular washing and drying of anything your wear on your feet will remove bacteria and stale sweat.</p>
<p>Bamboo has a natural antimicrobial effect (meaning it may have some ability to slow bacteria or mould growing), and socks made from this fibre <a href="https://www.tandfonline.com/doi/abs/10.1080/00405000.2011.614742">may be helpful</a>, but it’s <a href="https://consumer.ftc.gov/articles/bamboo-fabrics">unclear</a> whether the benefits <a href="http://mistrafuturefashion.com/bamboo-fibers-anti-bacterial-quality-a-misconception/">translate to bamboo clothing products</a>.</p>
<p>There’s <a href="https://www.taylorfrancis.com/chapters/edit/10.1201/9781003141426-4/axillary-odour-formation-retention-role-textiles-fibers-fabric-structure-rathinamoorthy-thilagavathi">conflicting</a> <a href="https://www.sciencedirect.com/science/article/pii/S1110016818301327">views</a> <a href="https://www.researchgate.net/publication/342480090_Influence_of_Moisture_Management_Properties_on_Socks_Made_from_Recycled_Polyester_Virgin_Cotton_and_its_Blends_FIBRES_TEXTILES_in_Eastern">on</a> the best material for shoes and socks to improve smelly feet, so more research is needed. </p>
<p><div data-react-class="Tweet" data-react-props="{"tweetId":"1519552835553468416"}"></div></p>
<h2>Treatments for sweaty and smelly feet</h2>
<p>If your feet are stubbornly sweaty and smelly even with good foot hygiene and attention to footwear, you may need to consider some other options.</p>
<p>An expert opinion from a podiatrist will help you make an appropriate treatment choice and ensure more serious issues aren’t missed.</p>
<p>Most of the available treatments for body odour target sweat production:</p>
<ul>
<li><p>a strong <a href="https://www.racgp.org.au/afp/2013/may/hyperhidrosis-and-bromhidrosis">antiperspirant</a> containing aluminium chloride hexhydrate, which can be purchased from a pharmacy without a prescription and applied directly to your feet </p></li>
<li><p>“<a href="https://dermnetnz.org/topics/iontophoresis">iontophoresis</a>” is a procedure offered at specialist clinics to reduce sweating in the hands and feet. A mild electrical current is passed through skin soaked in tap water. <a href="https://dermnetnz.org/topics/iontophoresis">One study</a> found around 75–80% of participants had reduced foot sweating after 20 days of this treatment</p></li>
<li><p><a href="https://www.racgp.org.au/afp/2013/may/hyperhidrosis-and-bromhidrosis">Botox</a> treatments are highly effective in reducing foot sweating. Botox works by blocking the nerves that activate sweat glands. However, injections into the sole of your foot can be very uncomfortable</p></li>
<li><p>a topical cream containing a small amount of “glycopyrronium bromide” <a href="https://dermnetnz.org/topics/anticholinergic-medications">can help</a> to control excessive sweating.</p></li>
</ul>
<hr>
<p><em>Caroline Robinson would like to thank Anna Horn from Charles Sturt podiatry, for her contribution to researching this article.</em></p><img src="https://counter.theconversation.com/content/184561/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Caroline Robinson is affiliated with the Australasian Council of Podiatry Deans and the Australian Podiatry Association.
She'd like to thank Anna Horn from Charles Sturt podiatry, for her contribution to researching this article.</span></em></p>Fresh sweat doesn’t have a smell. It’s the bacteria that feast on sweat that cause the bad smell.Caroline Robinson, Associate Professor Podiatry, Charles Sturt UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1807242022-06-08T10:02:50Z2022-06-08T10:02:50ZCOVID: six ways long-term smell loss can affect you<figure><img src="https://images.theconversation.com/files/466040/original/file-20220530-16-ipylp2.jpg?ixlib=rb-1.1.0&rect=0%2C0%2C5472%2C3645&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Losing your sense of smell can have a range of effects.</span> <span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/sick-woman-trying-sense-smell-half-2074289665">Photoroyalty/Shutterstock</a></span></figcaption></figure><p>Early in the pandemic, multiple studies showed that <a href="https://academic.oup.com/chemse/article/45/9/865/5912953?login=false">about half of people</a> with COVID lost their sense of smell (called anosmia) at some point during the course of infection. Roughly an additional <a href="https://pubmed.ncbi.nlm.nih.gov/33219539/">20% to 35%</a> experienced a clinical reduction in their ability to smell (hyposmia). </p>
<p>Although <a href="https://pubmed.ncbi.nlm.nih.gov/35170099/">more recent evidence</a> suggests omicron might not lead to smell loss as much as earlier variants, given that more than <a href="https://coronavirus.jhu.edu/map.html">half a billion people</a> have had at least one of the variants to date, that’s still many millions of people who have probably experienced this condition to some degree.</p>
<p>For most, this is only a temporary loss of function. But a sizeable portion will experience longer-term problems. Recent studies show that 12 to 18 months after the initial COVID diagnosis, <a href="https://www.medrxiv.org/content/10.1101/2022.01.20.22269490v1">34%</a> to <a href="https://pubmed.ncbi.nlm.nih.gov/34553706/">46%</a> of people are still experiencing a clinical reduction in their sense of smell. Most of these people are, however, <a href="https://pubmed.ncbi.nlm.nih.gov/32301284/">not aware of</a> this. </p>
<p>A related issue is parosmia, where a person’s perception of odours change, often finding they become more unpleasant. Research suggests that <a href="https://pubmed.ncbi.nlm.nih.gov/35398877/">up to 47%</a> of people who have had COVID could be affected. As with smell loss, most people with parosmia will likely heal over time. Yet some could have longer-lasting problems.</p>
<p>COVID isn’t the only condition that can lead to smell loss. For example, it can <a href="https://pubmed.ncbi.nlm.nih.gov/23875929/">also be caused</a> by other viruses or infections, head trauma, or a range of neurodegenerative diseases. While the evidence on post-COVID smell loss is still emerging, data from other types of olfactory dysfunction gives us an idea of some of the effects that long-term smell loss can have on everyday life.</p>
<p><strong>1. Food safety</strong></p>
<p>People with this impairment are more likely to ingest spoiled food because it’s the smell, first and foremost, that warns us when something has gone off. This can increase the risk of food-borne illensses.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/coronavirus-loss-of-smell-and-taste-reported-as-early-symptoms-of-covid-19-134564">Coronavirus: loss of smell and taste reported as early symptoms of COVID-19</a>
</strong>
</em>
</p>
<hr>
<p><strong>2. Taste</strong></p>
<p>Other than the core taste sensations (sweet, salty, bitter, sour and umami), nearly all of what we experience as taste is produced by odours reaching the odour receptors in the nose via the <a href="https://pubmed.ncbi.nlm.nih.gov/16028032/">oral-nasal passage</a> in the back of the throat. Unfortunately, without a sense of smell, most of what you eat will have little to no taste. Remove the ability to sense odours and an apple will taste just like a potato if you close your eyes. </p>
<p><strong>3. Appetite</strong></p>
<p>Beyond giving us pleasure when eating, food odours also <a href="https://www.sciencedirect.com/science/article/pii/B9780123743879000027">trigger our appetite</a>. This means that when we can’t smell the aromas of dinner cooking in the oven, we’re less likely to get hungry. </p>
<figure class="align-center ">
<img alt="A man looks at a burger." src="https://images.theconversation.com/files/466069/original/file-20220530-16-7hohhq.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/466069/original/file-20220530-16-7hohhq.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/466069/original/file-20220530-16-7hohhq.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/466069/original/file-20220530-16-7hohhq.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/466069/original/file-20220530-16-7hohhq.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/466069/original/file-20220530-16-7hohhq.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/466069/original/file-20220530-16-7hohhq.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">People with smell loss are less able to taste their food.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/man-eating-restaurant-enjoying-delicious-food-331355027">Estrada Anton/Shutterstock</a></span>
</figcaption>
</figure>
<p><strong>4. Fluctuations in weight</strong></p>
<p>The combined loss of appetite and pleasure from eating makes most people with a newly acquired smell disorder <a href="https://pubmed.ncbi.nlm.nih.gov/15064063/">lose weight</a>, initially. Our bodies are, however, designed to keep us alive. People with smell loss quickly begin seeking pleasure from other sensory stimuli when eating, such as texture, for instance in the crunchiness of fried food. And instead of waiting until they are hungry, many will simply eat more often. These non-conscious changes in <a href="https://pubmed.ncbi.nlm.nih.gov/17975508/">eating behaviour</a> often result in weight gain, which can lead to long-term heart problems and other related health issues.</p>
<p><strong>5. Relationships</strong></p>
<p>There are some consequences of smell loss you might not immediately think about. Take for example the fact that a person who can’t smell won’t be able to monitor their own body odour. This can be a source of self-consciousness and insecurity in <a href="https://academic.oup.com/chemse/article/39/3/185/502849?login=false">social situations</a>.</p>
<p><a href="https://academic.oup.com/chemse/article/39/3/185/502849?">Several studies</a> have demonstrated that a poor sense of smell is linked with a reduction in reported social interactions, number of friends and sexual enjoyment. The latter could also be related to the loss of ability to sense the scent of a partner.</p>
<p><strong>6. Mental health</strong></p>
<p><a href="https://link.springer.com/article/10.1007/s00441-020-03381-9">One-third</a> of people seeking treatment for their smell problems report experiencing a reduction in their quality of life and general wellbeing, compared with before they were having these problems. This is likely due to a combination of the factors outlined above. People with smell dysfunction often report <a href="https://pubmed.ncbi.nlm.nih.gov/27393116/">symptoms of depression</a>, and it’s not uncommon that they link these to their smell problems.</p>
<h2>Treatment options</h2>
<p>Sadly, few treatments exist for people experiencing smell dysfunction. For virus-induced smell problems, the only treatment that has some demonstrable effect is <a href="https://academic.oup.com/chemse/article/42/7/513/3844730?login=false">smell training</a>. This is a bit like physiotherapy for the nose and consists of exposure therapy, where the patient is asked to smell a range of odours for about 20 minutes, each morning and evening, over a period of two to three months. Although patients will seldom make a complete recovery, studies have shown that smell training does <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8984764/">improve olfactory functions</a> with time.</p>
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Read more:
<a href="https://theconversation.com/four-strange-covid-symptoms-you-might-not-have-heard-about-181217">Four strange COVID symptoms you might not have heard about</a>
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<p>That said, the COVID pandemic has given olfactory research a push forward, and several interesting new treatments are currently in pre-clinical trials. Within a few years, it’s possible that we will see a range of novel treatments for smell dysfunction.</p>
<p>In the meantime, what should you do if you think your sense of smell isn’t as it should be? You can start smell training yourself using common household odours. If you don’t see a noticeable improvement after six weeks of training, get in touch with your healthcare provider for an evaluation.</p><img src="https://counter.theconversation.com/content/180724/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Johan N. Lundström is a faculty member of the non-profit research center the Monell Chemical Senses Center, Philadelphia, as well as a Senior advisor to the Stockholm University Brain Imaging Center and the Ear-Nose-Throat Clinic at the Karolinska University Hospital. He currently receives funding from the Knut and Alice Wallenberg Foundation, the Swedish Research Council, the European Research Council, the National Institute of Health, the Swedish Research Council for Sustainable Development, and the Bygg-Göta Foundation.</span></em></p>Many people have been left with longer-term impairments to their sense of smell following COVID.Johan N. Lundström, Associate Professor, Department of Clinical Neuroscience, Karolinska InstitutetLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1833632022-05-20T00:41:00Z2022-05-20T00:41:00ZCan sniffer dogs really detect COVID almost as well as a PCR test? Turns out they can<figure><img src="https://images.theconversation.com/files/464382/original/file-20220519-26-gkluh1.jpg?ixlib=rb-1.1.0&rect=2%2C2%2C1914%2C1273&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><a class="source" href="https://unsplash.com/photos/N04FIfHhv_k">Victor Grabarczyk/unsplash</a></span></figcaption></figure><p>Dogs have an exceptional sense of smell. We take advantage of this ability in many ways, including by training them to find illicit drugs, dangerous goods and even people. </p>
<p>In recent years, a dog’s sense of smell has also been used in the medical field. These remarkable animals can be trained to <a href="https://theconversation.com/the-scent-of-sickness-5-questions-answered-about-using-dogs-and-mice-and-ferrets-to-detect-disease-151832">sniff out</a> cancer, diabetes, and extraordinarily, <a href="https://www.nature.com/articles/s41598-019-40721-4">epileptic seizures</a> before they occur.</p>
<p>Early in the pandemic the possibility of using dogs to sniff out COVID was explored in a few countries. And although the results of these early trials surpassed most people’s expectations, many <a href="https://theconversation.com/yes-dogs-can-sniff-out-covid-but-not-after-dinner-when-they-need-a-nap-161669">questions remained</a>. These included how well these findings would stand up to more rigorous scientific scrutiny and how well dogs would perform outside the artificial environment of the research laboratory.</p>
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Read more:
<a href="https://theconversation.com/yes-dogs-can-sniff-out-covid-but-not-after-dinner-when-they-need-a-nap-161669">Yes, dogs can sniff out COVID. But not after dinner, when they need a nap</a>
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<p>In the past week we have moved closer to answering these questions, with an article published in <a href="https://gh.bmj.com/content/7/5/e008024">BMJ Global Health</a>, which found dogs could detect COVID almost as well as PCR tests, in some circumstances.</p>
<p><div data-react-class="Tweet" data-react-props="{"tweetId":"1526676331735425026"}"></div></p>
<h2>What did the researchers test?</h2>
<p>This article reported the results of two studies. In both studies, four dogs were tested to see how well they detected COVID from skin swabs taken from people with or without COVID (according to the gold-standard test, PCR). </p>
<p>These dogs didn’t just come off the streets; they had already had a significant amount of training in sniffing out drugs, dangerous goods or cancer.</p>
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Read more:
<a href="https://theconversation.com/the-scent-of-sickness-5-questions-answered-about-using-dogs-and-mice-and-ferrets-to-detect-disease-151832">The scent of sickness: 5 questions answered about using dogs – and mice and ferrets – to detect disease</a>
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<h2>The first study</h2>
<p>In the first study, the researchers looked at whether the dogs could identify COVID in the skin swabs of 420 volunteers, 114 of whom had tested positive to COVID by PCR. </p>
<p>The study was rigorous, with various precautions against the results being compromised. This included an elaborate study protocol that involved a number of separate assistants and a dog handler. None of them knew whether the sample was from someone with COVID, so they could not influence the outcome, intentionally or unintentionally.</p>
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<a href="https://images.theconversation.com/files/464205/original/file-20220519-25-h91ovr.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="German Shepherd dogs with trainers" src="https://images.theconversation.com/files/464205/original/file-20220519-25-h91ovr.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/464205/original/file-20220519-25-h91ovr.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/464205/original/file-20220519-25-h91ovr.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/464205/original/file-20220519-25-h91ovr.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/464205/original/file-20220519-25-h91ovr.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/464205/original/file-20220519-25-h91ovr.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/464205/original/file-20220519-25-h91ovr.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
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<span class="caption">Neither the dog handler or assistants knew who had COVID and who didn’t.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/airport-security-workers-two-german-shepherd-1798027411">Shutterstock</a></span>
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<p>The dogs detected COVID with a sensitivity of 92% (which refers to their ability to correctly identify those with infection) and a specificity of 91% (their ability to correctly identify those without infection). </p>
<p>Although there was some variation between dogs, they all performed exceptionally well. There are no significant disclaimers here, this was a great result.</p>
<h2>The second study</h2>
<p>The second study was important as its goal was to see how well the dogs could do in the messiness of the real world. This real-life trial involved the dogs sniffing 303 incoming passengers at Helsinki-Vantaa International Airport in Finland. Each passenger also took a PCR test. </p>
<p>The dogs matched the PCR results in 296 out of 303 (98%) of the samples and they correctly identified the swabs as negative in 296 out of 300 (99%) samples.</p>
<p>The important consideration in interpreting this result is this happened during airport screening, a situation where you wouldn’t expect many people to test positive.</p>
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<a href="https://images.theconversation.com/files/464207/original/file-20220519-14-ilb0td.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Sniffer dog resting on airport baggage carousel" src="https://images.theconversation.com/files/464207/original/file-20220519-14-ilb0td.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/464207/original/file-20220519-14-ilb0td.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/464207/original/file-20220519-14-ilb0td.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/464207/original/file-20220519-14-ilb0td.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/464207/original/file-20220519-14-ilb0td.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/464207/original/file-20220519-14-ilb0td.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/464207/original/file-20220519-14-ilb0td.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
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<span class="caption">Sometimes tired doggies just need a bit of a lie down.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/drug-detection-dog-airport-view-621943664">Shutterstock</a></span>
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<p>In this type of low-prevalence environment, you want dogs to be able to screen passengers with a high “negative predictive value”. That is, you want the dogs to be able to identify people who are not carrying the virus to differentiate them from those who may be carrying it. Then you would carry out confirmatory PCR testing on that last group.</p>
<p>In an environment where the prevalence of COVID is around 1%, such as an airport, the researchers estimated the “negative predictive value” for dogs screening for COVID to be 99.9%. That is, the dogs would be expected to correctly exclude 99.9% of passengers as having COVID. This is another fantastic result.</p>
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Read more:
<a href="https://theconversation.com/want-to-cut-your-chance-of-catching-covid-on-a-plane-wear-a-mask-and-avoid-business-class-180333">Want to cut your chance of catching COVID on a plane? Wear a mask and avoid business class</a>
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<h2>Low tech and instant</h2>
<p>In a world where we rely on expensive technological solutions, there is something reassuring about finding a low-tech option for screening COVID. </p>
<p>Importantly, however, the study highlights dogs are quick to train for this task and are ideal for screening in high-throughput settings, such as airports, given how accurate they are and the fact they give instant results.</p>
<p>Although nothing should surprise us about our closest friend, another incredible outcome from this study was the suggestion the dogs may have been able to distinguish between the variants of SARS-CoV-2, the virus that causes COVID. </p>
<p>While other possible explanations cannot be excluded, the performance of the dogs seemed to drop with the emergence of the Alpha variant. This was attributed to the dogs being able to identify a difference between this variant and the wild-type virus on which they were originally trained. </p>
<p>These studies confirm nothing could be further from the truth when we say you can’t teach an old dog new tricks.</p>
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Read more:
<a href="https://theconversation.com/why-are-there-so-many-new-omicron-sub-variants-like-ba-4-and-ba-5-will-i-be-reinfected-is-the-virus-mutating-faster-182274">Why are there so many new Omicron sub-variants, like BA.4 and BA.5? Will I be reinfected? Is the virus mutating faster?</a>
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<img src="https://counter.theconversation.com/content/183363/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Hassan Vally does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>With the right training, dogs can sniff out more than 90% of COVID cases.Hassan Vally, Associate Professor, Epidemiology, Deakin UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1775832022-03-10T11:28:40Z2022-03-10T11:28:40ZIf you love ASMR you might be more sensitive, our research finds<p>Do you ever experience a tingling sensation in your scalp when someone whispers? </p>
<p>If you recognise that feeling, then you may well be acquainted with the phenomenon that’s gathered millions of followers over the last few years, and has been dubbed “autonomous sensory meridian response” (<a href="https://theasmr.com/what-is-asmr-meaning/">ASMR</a>). </p>
<p>For those of you who haven’t heard of ASMR, it’s a relaxing head-orientated tingling sensation that some people experience in response to various sensory “triggers”. It could be watching someone brush hair, or fold laundry with care and expertise or certain sounds like whispering or tapping. And in everyday life, one of the most common triggers is actually soft touch – like stroking someone’s arm or tracing fingers on the back.</p>
<p>Some people <a href="https://www.ncbi.nlm.nih.gov/books/NBK453209/#:%7E:text=Their%20results%20indicated%20that%20the,effect%20of%20ASMR%20on%20mood">report experiencing</a> ASMR for “as long as they can remember” – but the explosion of <a href="https://ahrefs.com/blog/top-youtube-searches/">online ASMR videos</a> is allowing people to tap into the sensation on-demand rather than having to wait for it to happen as they go about their daily lives. And many people (even those that don’t experience ASMR tingling) may use them for relaxation and sleep. </p>
<p>But an intriguing question that remains unanswered is why only some people experience ASMR tingling.</p>
<p>We recently conducted <a href="https://www.sciencedirect.com/science/article/abs/pii/S0092656621001203">a study</a> which goes some way towards answering this question. It seems that people who experience ASMR have heightened sensory sensitivity – that is, they are more sensitive to what’s going on around them, and inside them. Here’s how we found out, and what it means.</p>
<h2>Sensitivity explained</h2>
<p>We all differ in <a href="https://www.tandfonline.com/doi/pdf/10.1080/17588928.2018.1557131?casa_token=yRKIJyIeo1AAAAAA:6yggeDHHK-H9JzT0ewFypPEfwhuVR-WymeFJOt18QqN5jAZkCt-hq2FMzCvokdC4pSWp-UkEkV9HsQ">how sensitive</a> we are to information from our five external senses (touch, sight, hearing, smell and taste). If you’re highly sensitive to external input you might be disgusted at the strong smell of an aftershave as you pass someone in the street, for example. </p>
<p>We also vary in sensitivity to our body’s internal state, such as whether we’re feeling hungry or cold. </p>
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Read more:
<a href="https://theconversation.com/differences-in-how-men-and-women-perceive-internal-body-signals-could-have-implications-for-mental-health-172917">Differences in how men and women perceive internal body signals could have implications for mental health</a>
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<p>So, to investigate whether people with ASMR are more “sensitive”, we tested participants using the most commonly used measures of internal and external sensory sensitivity. The <a href="https://www.pearsonclinical.co.uk/store/ukassessments/en/Store/Professional-Assessments/Motor-Sensory/Adolescent-Adult-Sensory-Profile/p/P100009054.html">adult sensory profile</a>, for example, asked participants to rate their response in numerous situations (such as how well they work with background noise or whether they startle easily at unexpected or loud noises). </p>
<p>We also assessed whether participants experience ASMR when exposed to 16 common triggers, and if so, the strength of their ASMR response and how they experienced it.</p>
<h2>Sensitivity links to ASMR</h2>
<p>It turned out that people who experience ASMR showed much higher levels of sensory sensitivity than people without ASMR.</p>
<p>They report hypersensitivity and negative responses to external stimuli such as noise and movement, and are easily overstimulated by their environment. They also show higher levels of body awareness and greater sensitivity to internal bodily sensations – noticing how their body changes when they feel happy, for example.</p>
<p>And the strength of their ASMR response was also associated with heightened external sensitivity and greater control over their attention towards their body and emotional state. </p>
<p>We think that the concept of the “highly sensitive person” (<a href="https://www.sciencedirect.com/science/article/pii/S0149763418306250">HSP</a>) may be central for differentiating ASMR responders from non-responders. </p>
<p>Using a <a href="https://sensitivityresearch.com/about-sensitivity/">flower metaphor</a>, developed by researchers to distinguish between people who have different levels of sensitivity – both internal and to the external social environment, such as people and visual stimuli – our study found that 56% of ASMR responders were categorised as highly sensitive “orchids” (who do well in ideal conditions but badly in poor conditions) with only 12% categorised as the environmentally resilient “dandelions”. The remainder were “tulips” who lie somewhere in between. </p>
<p>This contrasts with other studies suggesting that highly sensitive orchids usually make up around <a href="https://www.nature.com/articles/s41398-017-0090-6">30% of the population</a>.</p>
<p>As people with ASMR are more likely to be classified as highly sensitive, that might go some way towards explaining why ASMR has been linked to empathy. HSPs process social information more deeply which is <a href="https://onlinelibrary.wiley.com/doi/pdf/10.1002/brb3.242">thought to underpin</a> their ability to be more attuned and responsive to others’ emotions and needs. Future research may find similar enhanced social and emotional processing abilities in people with ASMR, but this needs to be properly investigated. </p>
<p>ASMR has been shown to enhance feelings of <a href="https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0196645">social connection</a> and the strongest ASMR triggers often simulate situations involving interpersonal closeness, intimacy, and touch. It may be that people who experience ASMR also derive more emotional benefit from social interactions. One fascinating possibility is that the tingling of ASMR reflects the ability to simulate <a href="https://www.sciencedirect.com/science/article/abs/pii/S0149763408001723?casa_token=2hTSpDq2tc0AAAAA:Hpy-wHdfNID3u6-JOk_SVflJQ02lR9mdSmRqrQiXJDa1J4_Sc0erl5jjGDLmXpffj-6uEouKFnw">social touch</a> and its benefits – such as stress reduction and mental well-being – from non-tactile stimuli. </p>
<p>There is one intriguing paradox: the same people who experience and enjoy ASMR triggers can often also be repulsed by the same sounds in different circumstances. ASMR-sensitive people have <a href="https://peerj.com/articles/3846/">elevated levels</a> of misophonia (a condition describing aversive and <a href="https://pubmed.ncbi.nlm.nih.gov/28561277/">angry feelings</a> in response to certain sounds, such as tapping, chewing or lip smacking), with 43% experiencing it. </p>
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Read more:
<a href="https://theconversation.com/asmr-what-we-know-so-far-about-this-unique-brain-phenomenon-and-what-we-dont-135106">ASMR: what we know so far about this unique brain phenomenon – and what we don't</a>
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<p>If the same trigger sounds elicit opposite emotional reactions in the same people, then this could mean that there isn’t anything inherently pleasant or unpleasant about the sounds themselves. </p>
<p>Our findings suggest that one reason for this seemingly odd co-occurrence might be because both ASMR and misophonia are underlined by increased sensory sensitivity, especially to sound. The situation, and how the sensory information is translated into an emotional response, might then determine whether the same sound is evaluated as positive or negative by the same person. Being sensitive has many benefits – but as with all things in life, it has its complications too.</p><img src="https://counter.theconversation.com/content/177583/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Giulia Poerio does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>It’s intriguing how some people experience ASMR while others don’t - our latest research suggests that many ASMR responders are highly sensitive “orchids”.Giulia Poerio, Associate lecturer, University of EssexLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1738112022-01-25T13:27:01Z2022-01-25T13:27:01ZFrom odor to action – how smells are processed in the brain and influence behavior<figure><img src="https://images.theconversation.com/files/441580/original/file-20220119-23-1y38fqx.jpg?ixlib=rb-1.1.0&rect=0%2C0%2C2734%2C1342&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">The compact olfactory system provides a more accessible way to study the brain as a whole.</span> <span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/photo/close-up-of-a-dogs-nose-royalty-free-image/603137803">Esther Kok/EyeEm via Getty Images</a></span></figcaption></figure><p>A dog raises its nose in the air before chasing after a scent. A mosquito zigzags back and forth before it lands on your arm for its next meal. What these behaviors have in common is that they help these animals “see” their world through their noses.</p>
<p>While humans primarily use their vision to navigate their environment, the vast majority of organisms on Earth communicate and experience the world through <a href="https://doi.org/10.1016/j.neuron.2005.10.022">olfaction</a> – their sense of smell.</p>
<p><a href="https://scholar.google.com/citations?user=wn_f7y0AAAAJ&hl=en">We</a> <a href="https://scholar.google.com/citations?user=JEi-fdoAAAAJ&hl=en">are</a> <a href="https://www.bbe.caltech.edu/people/elizabeth-j-hong">members</a> <a href="https://scholar.google.com/citations?user=GpkJjVUAAAAJ&hl=en">of</a> <a href="https://www.odor2action.org">Odor2Action</a>, an international network of over 50 scientists and students using olfaction to study brain function in animals. Our goal is to understand a fundamental question in neuroscience: How do animal brains translate information from their environments to changes in their behaviors?</p>
<p>Here, we trace the interconnections between smells and behaviors – looking at how behavior influences odor detection, how the brain processes sensory information from smells and how this information triggers new behaviors.</p>
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<figcaption><span class="caption">Visualizing what smells look like helps researchers design technologies that detect odors as well as a dog can.</span></figcaption>
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<h2>Detecting odors in the environment</h2>
<p>When the odor of a flower is released into the air, it takes the shape of a wind-borne <a href="https://doi.org/10.1007/s003480000263">cloud of molecules called a plume</a>. It encounters physical obstacles and temperature differences as it flows through space. These interactions create turbulence that splits the odor plume into thin threads that spread out as the scent moves away from its source. These filaments eventually reach an animal’s nose or an insect’s antenna.</p>
<p>Odors that are broken up into filaments present a challenge to animals using them to find food or mates or avoid threats. It becomes difficult to predict precisely where the odor is coming from. Is the source directly ahead, to the left or right, above or below?</p>
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<figcaption><span class="caption">This video by the Crimaldi Laboratory of the University of Colorado Boulder shows an odor plume developing behind a moving source over time. The source moves up and down from the left side, and the odor flows from left to right.</span></figcaption>
</figure>
<p>To work around this, animals have evolved what are called <a href="https://doi.org/10.1007/s10827-021-00798-1">active sensing</a> behaviors that improve their ability to detect and find odors in the environment.</p>
<p>When a fly detects the smell of fruit or a mosquito detects carbon dioxide from a possible host, for example, both insects first move upwind to get closer to the odor of the food source. They then move in a meandering, back-and-forth motion called casting to find more odor threads before surging upwind again. If they lose the scent, they’ll start casting again until they find the scent. Larger animals, such as mice and dogs, also alternate between more directed movements and more exploratory searching actions. </p>
<p>Animals also move their noses and antennae to improve the chances that they’ll encounter an odor. This is why dogs raise their noses in the air to increase the amount of odor they can sniff, and why insects move their antennae to stir up and penetrate the air to make better contact with odor molecules. </p>
<p>Once information from odors tell the animal that they’re close to the source, visual searching then comes into play.</p>
<h2>Making sense of odors</h2>
<p>When an animal comes into contact with an odor plume, it detects the presence of these odor molecules through tiny proteins called <a href="https://www.nobelprize.org/prizes/medicine/2004/summary/">odorant receptors</a>. These receptors are embedded in the sensory neurons lining its nasal cavity or antennae.</p>
<p>Each sensory neuron contains only one type of odorant receptor. And each type of odorant receptor has a different shape and set of chemical properties that determine which odors can bind to and activate it. Most of these receptors recognize multiple odors, and most odors can bind to multiple different receptors. What encodes the identity of a specific odor in the brain is determined by which combination of receptors are activated, and their relative strength of activation.</p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/MyHR6a-zJM0?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">This video from the Wachowiak Lab at the University of Utah shows the activity of the olfactory bulb in a mouse brain as the mouse is exposed to different odors. Different odors make different combinations of neurons in the olfactory bulb light up.</span></figcaption>
</figure>
<p>An animal like a mouse has about a <a href="https://doi.org/10.1016/j.neuron.2005.10.022">thousand types</a> of odorant receptors. Having a large number of these receptors with diverse shapes allows the system to detect and distinguish between a very large number of chemically unique odors, including ones the animal has never encountered before. Most odors in the environment are often a mix of many different types of molecules. The smell of some <a href="https://doi.org/10.1146/annurev.ecolsys.38.091206.095601">flowers</a> can be a blend of over 100 different chemical compounds.</p>
<p>Once an odor molecule binds to a receptor, sensory neurons send specific <a href="https://nba.uth.tmc.edu/neuroscience/m/s2/chapter09.html">electrical signals</a> into compartments of the brain called <a href="https://doi.org/10.3389/fncir.2014.00098">olfactory glomeruli</a>. Different odors elicit distinct patterns of electrical activity across these regions, and this generates a specific neural representation of the odor in the brain.</p>
<p>An important step toward understanding olfaction is figuring out how different classes of odors map to different patterns of electrical signals in the brain.</p>
<p>Neuroscientists hypothesize that as these signals undergo successive stages of processing deep in the brain, sensory representations of odor are <a href="https://doi.org/10.1146/annurev-neuro-071013-013941">reformatted</a> in ways that extract information most useful to survival. This could be whether the smell is coming from something nutritious, indicating a potential source of food, or it could help the animal identify whether the smell is coming from a potential competitor or predator.</p>
<p>These reformatted sensory representations form the basis for how animals perceive smell and determine what actions they take in response to this information.</p>
<h2>From odor to action</h2>
<p>Once information about a particular odor reaches the brain, it often elicits both instinctual and learned <a href="https://doi.org/10.1523/JNEUROSCI.1668-18.2018">behaviors</a>. Odors that signal danger may trigger the animal to freeze or run away, while odors from a member of the same species may trigger the animal to mark its territory or initiate courtship. </p>
<p>In many cases, animals perform these tasks with incredible <a href="https://www.pbs.org/wgbh/nova/article/dogs-sense-of-smell/">precision and effectiveness</a>. It’s still common to use search dogs to find lost people and pigs to find truffles because available technologies aren’t capable of performing as well.</p>
<p>Animals achieve this level of performance not just because they’re able to detect and identify an odor. They’re also able to integrate odor features, like how intense the odor smells, with environmental clues, like wind direction, and internal cues, like hunger. All this information comes together to generate specific sequences of behaviors such as “face into the wind and then walk forward.”</p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/FLH36ML8IEU?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">Dogs rely on smells to provide long-distance information. Humans, on the other hand, use smells for short distances.</span></figcaption>
</figure>
<p>To understand how odor guides these behaviors, scientists measure or manipulate an animal’s brain activity as they perform specific actions. This is done using imaging, electrophysiology or <a href="https://doi.org/10.1038/nn.4091">optogenetics</a>, which selectively activates specific neurons by shining a light on them. These approaches allow researchers to understand how patterns of brain activity shift when an animal changes its behavior to chase after an odor, or how environmental and internal cues combine to produce a best guess on the location of its next meal. </p>
<h2>Leading science and technology by the nose</h2>
<p>The olfactory system offers a unique opportunity to understand how the brain processes environmental information and translates it to behavior. Compared to other areas of the brain, the olfactory circuit is simpler in structure and uses fewer stages of processing. Its relative simplicity is what allows scientists like us to study it from end to end and learn how the brain works as a whole.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/441622/original/file-20220119-15-1atg4u1.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A rescue worker with a service dog goes through the ruins of a residential house to search for survivors" src="https://images.theconversation.com/files/441622/original/file-20220119-15-1atg4u1.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/441622/original/file-20220119-15-1atg4u1.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=415&fit=crop&dpr=1 600w, https://images.theconversation.com/files/441622/original/file-20220119-15-1atg4u1.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=415&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/441622/original/file-20220119-15-1atg4u1.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=415&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/441622/original/file-20220119-15-1atg4u1.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=521&fit=crop&dpr=1 754w, https://images.theconversation.com/files/441622/original/file-20220119-15-1atg4u1.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=521&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/441622/original/file-20220119-15-1atg4u1.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=521&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Robots may one day be able to replace dogs in search and rescue situations.</span>
<span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/news-photo/rescue-worker-with-a-service-dog-goes-through-the-ruins-of-news-photo/1229115883">Valery Sharifulin/TASS via Getty Images</a></span>
</figcaption>
</figure>
<p>Understanding brain function through the lens of olfaction could also pave the way for transformative developments in engineering, neuroscience and public health. Our research should accelerate the development of robots with <a href="https://doi.org/10.1177%2F0278364908095118">electronic noses</a> that can use odors to search for <a href="https://doi.org/10.1016/j.sbsr.2019.100305">chemical weapons</a>,
<a href="https://www.reuters.com/world/us/divers-try-locate-source-reported-oil-spill-gulf-coast-guard-2021-09-05/">underwater oil spills</a>
and <a href="https://doi.org/10.3390/inventions5030028">natural gas</a> leaking from pipelines in environments where it may be tedious or dangerous for humans or animals to go. Robots might also be able to search for missing people or disaster victims, something typically done with <a href="https://www.popsci.com/scientists-want-to-build-robotic-sniffer-that-outperforms-search-dogs/">trained dogs</a>.</p>
<p>An exciting future in scientific and medical development, we believe, is right under our noses.</p>
<p>[<em>Over 140,000 readers rely on The Conversation’s newsletters to understand the world.</em> <a href="https://memberservices.theconversation.com/newsletters/?source=inline-140ksignup">Sign up today</a>.]</p><img src="https://counter.theconversation.com/content/173811/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>John Crimaldi receives funding from the National Science Foundation, the National Institutes of Health, and the Department of Defense.</span></em></p><p class="fine-print"><em><span>Brian H Smith receives funding from the National Science Foundation.</span></em></p><p class="fine-print"><em><span>Elizabeth Hong receives funding from the National Science Foundation, the National Institutes of Health, the Curci Research Foundation, and the Luce Foundation</span></em></p><p class="fine-print"><em><span>Nathan Urban receives funding from the National Science Foundation and the National Institutes of Health. </span></em></p>Understanding how the brain translates smells into behavior change can help advance search and rescue technology and treatments for neurological conditions.John Crimaldi, Professor of Civil, Environmental and Architectural Engineering, University of Colorado BoulderBrian H. Smith, Trustees of ASU Professor, Arizona State UniversityElizabeth Hong, Assistant Professor of Neuroscience, California Institute of TechnologyNathan Urban, Provost and Senior Vice President, Lehigh University Licensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1744772022-01-11T17:25:59Z2022-01-11T17:25:59ZWhen a smell evokes a memory: new research offers clues about how the two are linked in the brain<figure><img src="https://images.theconversation.com/files/439736/original/file-20220106-25-1dxpk6p.jpg?ixlib=rb-1.1.0&rect=8%2C8%2C5742%2C3819&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/senior-woman-smelling-flowers-garden-654442804">wavebreakmedia/Shutterstock</a></span></figcaption></figure><p>In an episode of the popular TV series Black Mirror called <a href="https://www.vox.com/culture/2017/12/29/16808458/black-mirror-crocodile-recap-season-4-review">Crocodile</a>, an investigator asks a witness to smell a bottle of beer. The aim is to refresh her memory of a crime scene (the crime took place near a brewery).</p>
<p>This might not exactly be standard practice, but our sense of smell, or olfaction, is known for its ability to elicit memories. We all know the feeling. A whiff of a particular scent can take you back to your grandmother’s kitchen, the night of your first dance, or the sea shore.</p>
<p>And think of “scent marketing”, where brand designers infuse “signature scents”, for example in fashion stores and hotel lobbies, to enhance brand recognition across the globe.</p>
<p>Neuroscientists studying olfaction have long wondered about <a href="https://doi.org/10.1016/s0166-2236(03)00076-6">the connection</a> between our sense of smell and memory. Is this relationship between memory and olfaction a result of the way the brain is wired? A study recently published in the journal <a href="https://www.nature.com/articles/s41586-021-04242-3">Nature</a> has broken important ground towards answering this longstanding question.</p>
<p>Before we look at the study, some background about how the brain facilitates our sense of smell. Scent molecules are initially detected by receptor neurons in the nose. The neurons send information about these encounters first to the <a href="https://www.britannica.com/science/olfactory-bulb">olfactory bulb</a>, a brain structure about the size of your fingertip located above the nasal cavity.</p>
<p>The olfactory bulb then sends signals to another brain structure called the <a href="https://www.sciencedirect.com/topics/neuroscience/piriform-cortex">piriform cortex</a>. It is believed odour recognition happens there – that is, we identify its potential source, like an apple, a banana, or freshly cut grass.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/six-curious-facts-about-smell-128533">Six curious facts about smell</a>
</strong>
</em>
</p>
<hr>
<h2>What the researchers did</h2>
<p>To study how the brain combines olfactory and spatial information, Cindy Poo and her colleagues at the Champalimaud Centre for the Unknown in Portugal had six rats complete a navigation task.</p>
<p>The rats had to repeatedly navigate a cross-shaped map with four corridors, as shown in the video below from about the two-and-a-half minute mark. At the beginning of each trial a light would point the rat down one of the corridors, where it would be exposed at random to one of four distinct smells (citrus, grass, banana or vinegar). The location of a water reward was dependent on which odour the rat was exposed to.</p>
<p>For example, the citrus odour meant the water reward was at the end of the south corridor. If the rat was exposed to the citrus smell in the east corridor, it would need to travel south for the reward. If it received the smell in the south corridor in the first instance, it could stay put and receive the reward. The idea was that with practice, a given smell would signal to the rat the location of the reward.</p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/BunEBiU3MO0?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
</figure>
<p>The surroundings of the maze were decorated with visual landmarks so the rats could also orientate themselves based on those landmarks. However, the rats’ starting point was different in each trial. If it had been fixed, they could theoretically just have memorised a sequence of turns to find the correct corridor, and not used any spatial memory at all. This meant that completing the task successfully relied on a combination of spatial navigation and olfaction. </p>
<p>After about three weeks of training the rats did quite well; they were able to locate the water reward in roughly 70% of trials. This indicates that the rats were able to combine their internal map of the environment with locations of smells to locate the reward.</p>
<h2>Looking at neuron activity</h2>
<p>Neurons in the hippocampus, a part of the brain involved in memory and navigation, are known for functioning as “place cells”. These are cells which <a href="https://www.nobelprize.org/prizes/medicine/2014/summary/">become active</a> at a specific location in an environment, which allows us to find our way around. Similar cells are also found in another part of the brain called the entorhinal cortex.</p>
<p>The most striking finding of the new study is that such location-selective cells are not only present in the hippocampus and entorhinal cortex, but also in a brain area linked primarily to olfactory function, namely the piriform cortex, the place thought to be primarily responsible for odour recognition.</p>
<p>The researchers in the study monitored the electrical activity of neurons in this area. Surprisingly, they found that only around 30% of neurons in this region of the rats’ brains responded to specific odours. Another 30% of neurons fired in response to both a particular smell and location. </p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/the-strange-science-of-odour-memory-74403">The strange science of odour memory</a>
</strong>
</em>
</p>
<hr>
<p>The remaining 40% of active neurons did not respond to specific odours at all, but rather to the locations where the rats had previously smelt the odours. These location-selective neurons would even start to fire when the rats were only just entering the corridor, before encountering any smell.</p>
<p>The researchers then wanted to understand whether the hippocampus and piriform cortex “talked” to each other while the rats were solving the puzzle. They found that cells in both regions tended to fire in synchrony while the rats were navigating the maze. </p>
<h2>So what does this tell us?</h2>
<p>These results show that the olfactory system may play a role in spatial navigation, and that spatial memory and olfactory information converge in the piriform cortex. But why has the brain evolved to represent location and odour in the same area?</p>
<p>The answer could be that odours are very useful clues for finding our way around. For example, a pine forest smells different from a meadow, while a fox’s burrow has a different smell to a rat’s nest. The rule holds even in man-made environments: an underground rail system smells different from a supermarket, an office different from a restaurant. </p>
<p>So our brains might be wired to associate smells with places because this has been useful in our evolutionary past.</p>
<p>This study was conducted in rats, which rely more on their sense of smell for navigation than humans do, since our perception is dominated by vision. But these findings do give new insights about how olfaction and spatial memory are likely connected in the human brain.</p><img src="https://counter.theconversation.com/content/174477/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Michael Schmuker receives funding from NSF/CIHR/DFG/FRQ/UKRI-MRC as a member of the Next Generation Networks for Neuroscience Program (NeuroNex), within the "Odor2Action" network (NSF award no. 2014217, MRC award no. MR/T046759/1), and the EU flagship Human Brain Project SGA3 (H2020 award no. 945539).</span></em></p>A smell will often take us back to a particular place and time. But how are place and smell linked in the brain?Michael Schmuker, Professor of Neural Computation, University of HertfordshireLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1423632021-06-16T12:35:58Z2021-06-16T12:35:58ZSmelling in stereo – the real reason snakes have flicking, forked tongues<figure><img src="https://images.theconversation.com/files/403812/original/file-20210601-15-15hx7un.jpg?ixlib=rb-1.1.0&rect=7%2C0%2C5121%2C3427&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Long misunderstood, snake tongues have fascinated naturalists for centuries.</span> <span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/photo/red-tailed-green-rat-snake-gonyosoma-oxycephalum-royalty-free-image/499911945">reptiles4all/iStock via Getty Images Plus</a></span></figcaption></figure><p>As dinosaurs lumbered through the <a href="https://www.britannica.com/science/Jurassic-Period">humid cycad forests of ancient South America</a> 180 million years ago, primeval lizards scurried, unnoticed, beneath their feet. Perhaps to avoid being trampled by their giant kin, some of these <a href="https://doi.org/10.1126/sciadv.1500743">early lizards sought refuge underground</a>. </p>
<p>Here they <a href="https://doi.org/10.1093/icb/15.2.455">evolved long, slender bodies and reduced limbs</a> to negotiate the narrow nooks and crevices beneath the surface. Without light, <a href="https://doi.org/10.2307/1439015">their vision faded</a>, but to take its place, an especially acute sense of smell evolved.</p>
<p>It was during this period that these proto-snakes evolved one of their most iconic traits – a <a href="https://theconversation.com/explainer-why-do-snakes-flick-their-tongues-29935">long, flicking, forked tongue</a>. These reptiles eventually returned to the surface, but it wasn’t until the extinction of dinosaurs many millions of years later that they <a href="https://doi.org/10.1186/s12862-015-0358-5">diversified into myriad types of modern snakes</a>.</p>
<p>As an <a href="https://scholar.google.com/citations?hl=en&user=G-2IS0oAAAAJ">evolutionary biologist</a>, I am fascinated by these bizarre tongues – and <a href="https://doi.org/10.1126/science.263.5153.1573">the role they have played in snakes’ success</a>.</p>
<h2>A puzzle for the ages</h2>
<p>Snake tongues are so peculiar they have fascinated naturalists for centuries. Aristotle believed the forked tips provided snakes a <a href="https://archive.org/details/worksofaristotle512aris">“twofold pleasure” from taste</a> – a view mirrored centuries later by French naturalist Bernard Germain de Lacépède, who suggested the twin tips could adhere more closely to “<a href="https://www.biodiversitylibrary.org/item/54321#page/9/mode/1up">the tasty body</a>” of the soon-to-be snack.</p>
<p>A 17th-century astronomer and naturalist, Giovanni Battista Hodierna, thought snakes used their tongues for “<a href="https://doi.org/10.1098/rstl.1683.0010">picking the dirt out of their noses … since they are always grovelling on the ground</a>.” Others contended the tongue captured flies “<a href="http://hdl.loc.gov/loc.gdc/lhbcb.27239">with wonderful nimbleness … betwixt the forks</a>,” or <a href="https://www.biodiversitylibrary.org/item/24612#page/7/mode/1up">gathered air for sustenance</a>.</p>
<p>One of the most persistent beliefs has been that the <a href="https://www.biodiversitylibrary.org/item/31811#page/5/mode/1u">darting tongue is a venomous stinger</a>, a misconception perpetuated by Shakespeare with his many references to “stinging” serpents and adders, “<a href="https://shakespeare.folger.edu/shakespeares-works/richard-ii/act-3-scene-2/?search=adder/#line-3.2.4">Whose double tongue may with mortal touch throw death upon thy … enemies</a>.”</p>
<p>According to the French naturalist and early evolutionist Jean-Baptiste Lamarck, snakes’ limited vision obliged them to use their forked tongues “<a href="https://www.journals.uchicago.edu/doi/pdfplus/10.1086/274830">to feel several objects at once</a>.” Lamarck’s belief that the <a href="https://www.biodiversitylibrary.org/item/31811#page/5/mode/1up">tongue functioned as an organ of touch</a> was the prevailing scientific view by the end of the 19th century.</p>
<h2>Smelling with tongues</h2>
<p>Clues to the true significance of snake tongues began to emerge in the early 1900s when scientists turned their attention to two bulblike organs located just above the snake’s palate, below its nose. Known as Jacobson’s, or vomeronasal, organs, <a href="https://doi.org/10.1016/S0169-5347(00)88953-3">each opens to the mouth through a tiny hole in the palate</a>. Vomeronasal organs are found in a variety of land animals, including mammals, but not in most primates, so humans don’t experience whatever sensation they provide.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/406283/original/file-20210614-126997-r2t1cy.PNG?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A diagram showing the location of the vomeronasal organ on a snake." src="https://images.theconversation.com/files/406283/original/file-20210614-126997-r2t1cy.PNG?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/406283/original/file-20210614-126997-r2t1cy.PNG?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=263&fit=crop&dpr=1 600w, https://images.theconversation.com/files/406283/original/file-20210614-126997-r2t1cy.PNG?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=263&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/406283/original/file-20210614-126997-r2t1cy.PNG?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=263&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/406283/original/file-20210614-126997-r2t1cy.PNG?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=330&fit=crop&dpr=1 754w, https://images.theconversation.com/files/406283/original/file-20210614-126997-r2t1cy.PNG?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=330&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/406283/original/file-20210614-126997-r2t1cy.PNG?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=330&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Tongue tips deliver odor molecules to the vomeronasal organ.</span>
<span class="attribution"><span class="source">Kurt Schwenk</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<p>Scientists found that vomeronasal organs are, in fact, an offshoot of the nose, lined with similar sensory cells that <a href="https://doi.org/10.1177/000348943404300311">send impulses to the same part of the brain as the nose</a>, and discovered that tiny particles picked up by the tongue tips ended up inside the vomeronasal organ. These breakthroughs led to the realization that snakes use their tongues to collect and transport molecules to their vomeronasal organs – not to taste them, but to smell them.</p>
<p>In 1994, I used film and photo evidence to show that when snakes sample chemicals on the ground, they separate their tongues tips far apart just as they touch the ground. This action allows them to sample odor molecules from <a href="https://doi.org/10.1126/science.263.5153.1573">two widely separated points simultaneously</a>. </p>
<figure>
<img src="https://cdn.theconversation.com/static_files/files/1596/ezgif.com-gif-maker.gif?1622555314">
<figcaption><span class="caption">Sampling two points at once. <i>Credit: Kurt Schwenk</i></span></figcaption>
</figure>
<p>Each tip delivers to its own vomeronasal organ separately, allowing the snake’s brain to assess instantly which side has the stronger smell. Snakes have two tongue tips for the same reason you have two ears – it provides them with directional or “stereo” smell with every flick – a skill that turns out to be extremely useful when following scent trails left by potential prey or mates.</p>
<p>Fork-tongued lizards, the legged cousins of snakes, do something very similar. But snakes take it one step farther.</p>
<h2>Swirls of odor</h2>
<p>Unlike lizards, when snakes collect odor molecules in the air to smell, they oscillate their forked tongues up and down in a blur of rapid motion. To visualize how this affects air movement, graduate student <a href="https://scholar.google.com/citations?hl=en&user=8jJWMBgAAAAJ">Bill Ryerson</a> and I used a laser focused into a thin sheet of light to illuminate tiny particles suspended in the air.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/404121/original/file-20210602-21-1tj11os.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A snake flicking its toungue through a veil of smoke creating two swirls." src="https://images.theconversation.com/files/404121/original/file-20210602-21-1tj11os.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/404121/original/file-20210602-21-1tj11os.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/404121/original/file-20210602-21-1tj11os.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/404121/original/file-20210602-21-1tj11os.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/404121/original/file-20210602-21-1tj11os.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/404121/original/file-20210602-21-1tj11os.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/404121/original/file-20210602-21-1tj11os.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=566&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Tongue-flicking creates small eddies in the air, condensing the molecules floating within it.</span>
<span class="attribution"><span class="source">Kurt Schwenk</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<p>We discovered that the flickering snake tongue generates two pairs of small, swirling masses of air, or vortices, that act like tiny fans, pulling odors in from each side and <a href="https://doi.org/10.1002/jez.725">jetting them directly into the path of each tongue tip</a>. </p>
<p>Since odor molecules in the air are few and far between, we believe snakes’ unique form of tongue-flicking serves to concentrate the molecules and accelerate their collection onto the tongue tips. Preliminary data also suggests that the airflow on each side remains separate enough for snakes to benefit from the same “stereo” smell they get from odors on the ground.</p>
<p>Owing to history, genetics and other factors, natural selection often falls short in creating optimally designed animal parts. But when it comes to the snake tongue, evolution seems to have hit one out of the park. I doubt any engineer could do better.</p>
<p>[<em>You’re smart and curious about the world. So are The Conversation’s authors and editors.</em> <a href="https://theconversation.com/us/newsletters/the-daily-3?utm_source=TCUS&utm_medium=inline-link&utm_campaign=newsletter-text&utm_content=youresmart">You can read us daily by subscribing to our newsletter</a>.]</p><img src="https://counter.theconversation.com/content/142363/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Kurt Schwenk receives funding from The National Science Foundation and The University of Connecticut</span></em></p>Two tongue tips are better than one – an evolutionary biologist explains why snakes have forked tongues.Kurt Schwenk, Professor of Ecology and Evolutionary Biology, University of ConnecticutLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1616692021-06-03T20:13:02Z2021-06-03T20:13:02ZYes, dogs can sniff out COVID. But not after dinner, when they need a nap<figure><img src="https://images.theconversation.com/files/403926/original/file-20210602-27-eqoov7.jpg?ixlib=rb-1.1.0&rect=2%2C2%2C991%2C714&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/little-cute-dog-sniffing-1675007974">from www.shutterstock.com</a></span></figcaption></figure><p>The idea of cute puppy dogs playing a role in leading us out of this pandemic is about as tantalising a story anyone could conjure up right now. </p>
<p>It’s the type of good-news story you see at the end of the evening news bulletin involving cute animals making us healthier or happier. This time it involves using sniffer dogs to detect COVID-19. </p>
<p>So is there anything to this?</p>
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<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/your-dogs-nose-knows-no-bounds-and-neither-does-its-love-for-you-148484">Your dog's nose knows no bounds – and neither does its love for you</a>
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</em>
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<p>The proposition is plausible. Dogs’ noses are amazing instruments, which is why we already use them to sniff out bombs, drugs and dead bodies.</p>
<p>A dog’s <a href="https://www.sciencedirect.com/science/article/abs/pii/S0168159105002194?via%3Dihub">sense of smell</a> is <a href="https://www.carecredit.com/vetmed/article/how-well-can-your-dog-smell/#:%7E:text=Scientists%20guess%20the%20dog's%20sense,times%20more%20acute%20than%20ours.&text=One%20of%20the%20reasons%20a,a%20dog%20has%20about%2050">tens of thousands of times</a> more acute than a human’s. It’s <a href="https://phoenixvetcenter.com/blog/214731-how-powerful-is-a-dogs-nose#:%7E:text=They%20possess%20up%20to%20300,40%20times%20greater%20than%20ours.&text=Dogs%20possess%20a%20sense%20of,most%20advanced%20man%2Dmade%20instrument">many times more sensitive</a> than the most sensitive equipment to detect odours. Dogs can also sniff out diseases <a href="https://theconversation.com/dogs-sensitive-noses-may-be-the-key-to-early-detection-of-lung-cancer-99575">such as</a> cancer and diabetes.</p>
<p>So can dogs sniff out COVID-19? Before examining the evidence, there’s no suggestion dogs would <a href="https://my.clevelandclinic.org/health/diagnostics/21462-covid-19-and-pcr-testing">replace the PCR test</a>, the best diagnostic test we have for COVID-19 presently.</p>
<p>Instead, researchers hope dogs will be used for mass screening. This might be useful for quickly picking out individuals with COVID-19 in large crowds, say at airports, sports stadiums or concerts.</p>
<p><div data-react-class="InstagramEmbed" data-react-props="{"url":"https://www.instagram.com/p/CPpeKTPtNDn/?utm_source=ig_web_copy_link","accessToken":"127105130696839|b4b75090c9688d81dfd245afe6052f20"}"></div></p>
<h2>How do we know if dogs are up to the job?</h2>
<p>The best way to evaluate the performance of a test (in this case a trained dog’s nose) is to compare its results with the best test available (in this case the PCR test). </p>
<p>We want to know how good dogs’ noses are at correctly identifying people who:</p>
<ul>
<li><p><em>have</em> COVID-19 (as determined by a PCR test), a measure known as sensitivity</p></li>
<li><p><em>don’t have</em> COVID-19 (as determined by a PCR test), a measure known as specificity.</p></li>
</ul>
<p>A good screening test will have both a high sensitivity and a high specificity. If a test has a low sensitivity, it will often misclassify people as not having the disease when they do (false negatives). And if a test has a low specificity it will often misclassify people as having the disease when they don’t (false positives).</p>
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<p>
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<strong>
Read more:
<a href="https://theconversation.com/is-your-dog-happy-ten-common-misconceptions-about-dog-behaviour-97541">Is your dog happy? Ten common misconceptions about dog behaviour</a>
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<h2>So how about those cute doggies?</h2>
<p>The great news is dogs seem to perform exceptionally well in screening for COVID-19. Two recent preliminary studies suggest they can do this with high sensitivity and high specificity. </p>
<p><a href="https://www.lshtm.ac.uk/media/49791">One study</a>, which has yet to be independently verified by other researchers (peer reviewed), involved training six dogs to alert their handlers when they detected the scent of COVID-19 on clothing from an infected person. This study found a sensitivity of 82-94% and a specificity of 76-92%.</p>
<p>A <a href="https://www.vet-alfort.fr/detection-de-la-covid-19-par-des-chiens-resultats-tres-prometteurs">second</a> <a href="https://www.the-scientist.com/news-opinion/dogs-the-new-covid-19-rapid-test-68792">study</a>, which was presented at a conference and again has not been independently verified, involved training nine dogs. They identified cases from pieces of fabric that had been wiped on people’s armpits and put in a jar. This found a sensitivity of 97% and a specificity of 91%. </p>
<p>Taken together, it seems dogs are very good at rapidly detecting individuals with COVID-19 and don’t often get it wrong.</p>
<p><div data-react-class="Tweet" data-react-props="{"tweetId":"1397397250419040262"}"></div></p>
<h2>But hang on a minute</h2>
<p>It’s important to temper our enthusiasm with the usual caveats: </p>
<ul>
<li><p>we need to interpret all study findings cautiously until they are independently verified by other researchers (peer reviewed)</p></li>
<li><p>it would give us more confidence in the findings if other researchers reproduced these findings using more people</p></li>
<li><p>there is a big difference between dogs detecting COVID-19 in the controlled laboratory environment and the real world, which is messy, chaotic and full of other smells and distractions. </p></li>
</ul>
<p>Yet, I think these results are promising enough to justify some serious tail wagging.</p>
<h2>How does it work out in the field?</h2>
<p>A <a href="https://www.irishtimes.com/life-and-style/health-family/sniffer-dog-trials-make-case-for-rapid-detection-of-covid-1.4576844">number of countries</a> <a href="https://apnews.com/article/asia-pacific-lifestyle-coronavirus-pandemic-science-health-facf2e85a67e985e87d71edd5307c181">are already looking</a> at using dogs to screen for COVID-19 out in the real world.</p>
<p>But there are a few important operational limitations, the kind only revealed when you move dogs out of the laboratory. According to a <a href="https://apnews.com/article/asia-pacific-lifestyle-coronavirus-pandemic-science-health-facf2e85a67e985e87d71edd5307c181">Thai researcher</a>:</p>
<blockquote>
<p>5pm is their dinner time. When it’s around 4.50, they will start to be distracted. So, you can’t really have them work anymore. And we can’t have them working after dinner either because they need a nap. </p>
</blockquote>
<p>These are limitations we can all relate to and shouldn’t detract from the cutest possible addition to our fight against COVID-19.</p><img src="https://counter.theconversation.com/content/161669/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Hassan Vally does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>Who’s a good doggie? Sniffer dogs might one day be able to screen people for COVID-19 in large crowds. But not when they’re hungry or need a good lie down.Hassan Vally, Associate Professor, La Trobe UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1585542021-04-09T11:02:44Z2021-04-09T11:02:44ZConcern is mounting about zombie companies: why that matters for the economic recovery<figure><img src="https://images.theconversation.com/files/394038/original/file-20210408-15-1fr9ryx.jpg?ixlib=rb-1.1.0&rect=0%2C112%2C4932%2C3832&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Some economists are worried about a growing army of 'zombie companies'. </span> <span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/group-zombie-over-burn-city-background-316312358">leolintang via Shutterstock</a></span></figcaption></figure><p><em>This is a transcript of episode 10 of The Conversation Weekly podcast “<a href="https://theconversation.com/the-zombie-company-problem-and-what-it-means-for-our-economies-podcast-158544">The zombie company problem and what it means for our economies</a>”. In this episode, why some economists are worried about a growing army of “zombie companies” with lots of debts – and what this could mean for the shape of our economies. And researchers have found a new way to prevent predators from eating endangered birds and their eggs – via a form of biological, psychological warfare.</em> </p>
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<p><em>NOTE: Transcripts may contain errors. Please check the corresponding audio before quoting in print.</em></p>
<p>Dan Merino: Hello and welcome to The Conversation Weekly.</p>
<p>Gemma Ware: This week, why some economists are worried about a growing army of companies with lots of debts – known as “zombie companies”. We speak to two experts on what this could mean for the shape of our economies. </p>
<p>Karl Schmedders: We will see bankruptcies and some of these companies will no longer exist by their own. </p>
<p>Dan: And I speak to a researcher who has found a new way to prevent predators from eating endangered birds and their eggs. It’s a bit of biological, psychological warfare.</p>
<p>Catherine Price: It’s just mucking with their minds and getting them to ignore what is actually the smell of the bird. </p>
<p>Dan: I’m Dan Merino in San Francisco.</p>
<p>Gemma: And I’m Gemma Ware in London and you’re listening to The Conversation Weekly, the world explained by experts. </p>
<p>Gemma: Some companies have done better out of the pandemic than others. There have been clear winners and losers. </p>
<p>Dan: Online retailers have been riding high as consumer patterns have shifted. Amazon of course, has had a stellar year. Zoom, share price through the roof. </p>
<p>Gemma: Pharmaceutical companies have had a good year too, particularly those who successfully developed their own coronavirus vaccines. </p>
<p>Dan: But, it’s been bad for huge swathes of the economy. </p>
<p>Dan: Physical retailers such as shops and department stores, airlines, hotels… anyone of course, whose business is tourism, and the service sector have all been hit pretty hard. </p>
<p>Gemma: Some of these companies were ticking along nicely before the pandemic. It’s the coronavirus restrictions that have really hurt their revenues, they’ve just not had enough money coming in to cover outgoing costs. But, with a solid foundation, these companies are pinning their hopes on the recovery.</p>
<p>But other companies went into the pandemic hampered by large debts – economists call these zombie companies. </p>
<p>Dan: Ooh, zombies. OK, why are we calling companies undead?</p>
<p>Gemma: Well these ones aren’t quite dead, and they’re not insolvent, but they’re just about alive. It’s a term used to describe what happened to many Japanese companies in the 1990s after a bad financial crash there, or to firms in Europe and the US after the 2008 financial crisis. </p>
<p>But now some economists are concerned about a new and growing army of zombie companies, exacerbated by the pandemic. I’ve spoken to two financial experts about all this, and about why the situation is harder for smaller companies than larger ones. </p>
<p>Karl Schmedders: My name is Karl Schmedders I’m a professor of finance at IMD, a small business school in Lausanne, Switzerland. </p>
<p>Gemma: Karl researches the relationship between the real economy and the financial markets. I asked him what a zombie company is.</p>
<p>Karl: Zombie company describes a company that may be even earning money from its operation. However, these earnings are not enough to make debt payments to pay back loans or to pay back the interest on loans that they received from banks, from other lenders, or in the general financial market through bonds, through these pieces of paper that are sold in the market to take on loans. </p>
<p>Gemma: The financial crisis caused by the pandemic has made life even worse for many of these firms – but many were in trouble before anyone had even heard the word COVID. </p>
<p>Now, there may be any number of reasons why one particular company isn’t doing very well at any particular time. But Karl points to interest rates as part of the problem for the current crop of zombie companies. In Europe and the US, they’ve never been so low for long. </p>
<p>Some places, including Japan, Switzerland and the eurozone, have even been living with negative interest rates for a few years now. </p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/negative-interest-rates-will-not-fix-the-global-economy-just-ask-switzerland-130718">Negative interest rates will not fix the global economy – just ask Switzerland</a>
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<p>All this means cheap cash. Companies have been able to borrow money from banks at low cost, and so many went on a borrowing and spending spree. </p>
<p>Karl: For years already, interest rates were very low, so it didn’t make sense on a short-term view for companies to hold a lot of cash for a rainy day. Why? Because they received no interest, or very little interest, and so shareholders or owners said that doesn’t make sense to hold a lot of cash in a bank account. Either spend it or give it back to us through dividends or share buybacks. </p>
<p>Gemma: A share buyback is when a company buys back its own shares on the stock market. This reduces the number of shares and in turn can increase a key metric, called earnings per share, which financial analysts watch very closely. Share buybacks can also push up the value of a company’s own stock – which is good for the shareholders.</p>
<p>Karl: And so that’s what a lot of companies did. They reduced their cash holdings because it didn’t make sense to hold cash. </p>
<p>Gemma: But some firms went even further. </p>
<p>Karl: Because money was so cheap, some company even borrowed money in order to buy back their shares. Let that idea sink in. Companies, borrowed money, because money was so cheap, because interest rates are so small. Then they use the borrowed money not to invest in research and development, not to buy other companies, they borrowed money to buy back their own shares in order to drive up the share price.
But at the same time, they were increasing their debt. And this is now the situation that’s happened before COVID-19 a lot. </p>
<p>Gemma: The problem isn’t that companies were buying back their own shares – this is a fairly common practice – but that some of the companies doing so were on shaky financial ground. They were spending borrowed money on their own shares, rather than investing it into in research and development or in an effort to become more productive.</p>
<p>Karl: What happened when COVID-19 occurred? Suddenly economic activity went down a lot. Some of these companies suddenly didn’t earn enough money anymore in order to pay back those loans. And now suddenly they’re in trouble and they become a type of this zombie company. </p>
<p>Gemma: So they’re inefficient because they’re trying to service the debt, they’re trying to pay the interest on their debt, but at the moment, they’ve hit a crunch point because they have no earnings to help service it? </p>
<p>Karl: That’s a beautiful summary, that’s exactly what’s happening. </p>
<p>Gemma: And are there specific sectors that are more affected than others? </p>
<p>Karl: Clearly we see these types of companies, in those areas where earnings have really fallen apart. One area that has been hit hard are the airlines. The airline business is asset intensive. Airplanes are very expensive, and airlines typically do not have the funds, the equity to pay for these airplanes in cash. So they have a lot of debt, but we all know, we are not allowed to fly. So airlines, are not earning enough money to pay these loans. </p>
<p>A leading example is in the United States, Delta Airlines, which is sort of an iconic company, which at <a href="https://www.bloomberg.com/news/articles/2020-11-17/america-s-zombie-companies-have-racked-up-1-4-trillion-of-debt">the same time is a zombie</a>. Then we also see a company such as Boeing. Boeing is selling airplanes. Nobody is buying airplanes right now. At the same time Boeing had a lot of these <a href="https://www.newsweek.com/boeing-airlines-under-fire-90-billion-share-buybacks-stoke-controversy-bailout-pleas-least-1493934">share buybacks in recent years</a>.</p>
<p>Gemma: The pain was also felt further down the supply chain.</p>
<p>Karl: Another area where we see this is in the oil industry. There was a drastic reduction in the demand for oil-based products. We all drove less in our cars. The airlines needed much less kerosene for their airplanes because they couldn’t fly. And so some of the oil companies, suddenly find themselves not earning enough money to cover their interest expenses. </p>
<p>Gemma: Are there any estimates of the size of this zombie problem in zombie companies around the world?</p>
<p>Karl: Before COVID, <a href="https://www.ft.com/content/cc31fe38-8adb-11ea-9dcb-fe6871f4145a">Morgan and Stanley came out with an estimate</a> that about one in six companies in the United States are zombies. Bloomberg <a href="https://www.bloomberg.com/news/articles/2020-11-17/america-s-zombie-companies-have-racked-up-1-4-trillion-of-debt">came up with a study</a> in November of 2020. They looked at Russell 3000 companies. These are the 3000 largest companies listed on the stock market in the US. </p>
<p>And they saw that more than a quarter – that’s a big number – more than one in four companies in their most recent business year had these problems, were zombies. For Europe there are similar numbers or maybe numbers slightly larger.</p>
<p>Karl: Although there are no official statistics on zombie companies globally, data suggests these figures are similar for other rich countries.</p>
<p>Karl: While I don’t like to speculate, I think we can say that somewhere between 20% and 30% are sort of the current estimates, by people observing these zombie firms around the world.</p>
<p>Gemma: When the pandemic hit, governments around the world stepped in to help companies through the crisis – whether they were healthy or not. Some central banks moved to buy up corporate bonds. </p>
<p>And governments around the world also gave out huge sums of state aid to companies in the form of grants, loans or employment support schemes such as furlough. </p>
<p>Karl: There are some cynics who even say that some zombie companies who paid out too many dividends, who took out too many loans, were saved through COVID-19. Because of this global shock of COVID-19, the central banks came in with so much money and supported the economy so much, that some companies who in under normal circumstances may have gone bankrupt have been saved. </p>
<p>Gemma: Do you believe that? </p>
<p>Karl: Yes. I believe that some companies, have been saved by very cheap money.</p>
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<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/attack-of-zombie-companies-dont-let-them-eat-bailouts-that-are-vital-to-restore-the-economy-139177">Attack of zombie companies: don't let them eat bailouts that are vital to restore the economy</a>
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<p>Gemma: In fact, data from the <a href="https://www.ft.com/content/ac2828ad-7930-43ef-a227-1cbd8ff8c018">International Monetary Fund</a> suggests that while a recession as drastic as the one we’re in one would usually be followed by a rise in bankruptcies, in the world’s 13 biggest economies, the number has actually fallen. </p>
<p>Still, concerns are growing about what will happen once governments around the world stop their pandemic support programmes. For some analysts, the situation looks precarious. Figures published this week indicated the default rate in Europe on corporate loans – the rate at which companies are not able to pay back their debts when they come due – has <a href="https://www.telegraph.co.uk/business/2021/04/04/default-rate-corporate-loans-has-doubled/">doubled over the past year</a>. I asked Karl what the prognosis is for zombie companies from here.</p>
<p>Karl: It will be a very difficult process to slow down the support of worldwide economies without causing another recession that then is caused by zombie company insolvencies. So, central banks and governments face a huge task when they decide to reduce and eventually completely take out their support.</p>
<p>Now, certainly we hope that companies with a viable business model will see a big increase in earnings after the end of the lockdowns, if economic activity resumes and that some companies then have big earnings again so that their debt to earnings ratio will decrease and they will survive. But clearly some companies won’t see that.</p>
<p>Gemma: How a company fares after the pandemic may depend on its size. To understand more, I reached out to Sandy Brian Hager. </p>
<p>Sandy Brian Hager: I’m a senior lecturer in international political economy at City University in London. And my main research focus concerns inequality and issues of corporate power.</p>
<p>Gemma: Sandy is particularly concerned about what’s been happening to smaller companies. Earlier this year, he <a href="https://www.tandfonline.com/doi/full/10.1080/13563467.2020.1865900">published new research</a> with his colleague Joseph Baines at King’s College in London tracking the performance of corporations listed on the US stock exchange over the past few decades. They ranked companies based on their overall revenues, and then divided them up – into the top 10% of large corporations, the next 40% of medium-sized ones – and then the bottom 50% of smaller corporations. It’s these smaller corporations that Sandy says we should be worried about. </p>
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Read more:
<a href="https://theconversation.com/giant-firms-have-a-hidden-borrowing-advantage-that-has-helped-keep-them-on-top-for-decades-new-research-153001">Giant firms have a hidden borrowing advantage that has helped keep them on top for decades – new research</a>
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<p>Sandy: So these aren’t, you know, your mom and pop corner stores if you will, these are more, generally larger than that.</p>
<p>Based on our research, we’ve shown that they’ve been suffering for decades now, in terms of their profitability. Because of their smaller and often negative profit rates they’re definitely not able to tap into corporate bond markets. They have to borrow from banks at a much higher rate as well.</p>
<p>Gemma: Larger corporations have benefited for a long time from what’s called a borrowing advantage.</p>
<p>Sandy: Quite simply they have better access to loans at favourable rates from the banks. They’re are also able to tap into corporate debt markets and borrow at very cheap rates on the bond market as well. That means that they’re able to borrow on a more favourable basis that allows them to consolidate their position within markets and continue to borrow at those favourable rates.</p>
<p>Gemma: Smaller companies, on the other hand are at a disadvantage because the loans they have access to are more expensive – they come with higher interest rates. That means they have to spend more of their hard-earned cash on paying them back.</p>
<p>Sandy: There’s a kind of vicious circle going on that we talk about in our research. We’ve shown that they have to borrow from banks at a much higher rate, and that obviously eats into their profits even more because they’re having to spend so much in terms of the amounts that they pay back to banks in the form of interest.</p>
<p>Gemma: Crucially, even during the pandemic, when the US government issued emergency loans to try and lessen the impact on the economy, Sandy says larger companies have been treated more favourably.</p>
<p>Sandy: If you look at, the intervention, for example, that we’ve seen in the United States, they’ve established a bunch of different lending facilities for companies of different sizes. So there’s the main street facilities that have been aimed at small- and medium-sized corporations. And then we have the corporate credit facilities that have been aimed at larger corporations. Federal Reserve has promised to prop up the corporate bond market by intervening and buying up debt if need be. And what we saw is that lending rates for larger corporations plummeted as a result and they went on a kind of borrowing spree through the pandemic. </p>
<p>Now, the main street facilities, they were meant to sort of help more smaller and medium-sized corporations. And the problem with the main street facilities is that a lot of the criteria that they established for companies to access them was really prohibitive. So a lot of the smaller companies were already in financial distress and they didn’t meet the requirements. Those companies that were eligible for the main street facilities, oftentimes they found that the administrative burden of accessing the facilities was just too high. So they’ve really been starved for financing through the pandemic. </p>
<p>Gemma: Karl says those companies that are in a more stable financial position may see this as an opportunity to acquire competitors that are struggling. And this will usher in a wave of mergers and acquisitions.</p>
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<a href="https://theconversation.com/takeovers-a-tidal-wave-of-buyouts-is-coming-in-2021-heres-what-it-means-152858">Takeovers: a tidal wave of buyouts is coming in 2021 – here's what it means</a>
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<p>Karl: Some of these companies may be competitors to healthy companies. And so these healthy companies say, “Oh, we can get a larger market share. So why don’t we buy this distressed company?” To get, sort of out of the zombie situation and reduce zombies, we will see bankruptcies, but we will also see some of these companies will no longer exist by their own, but then will be bought out by larger companies.</p>
<p>Gemma: The pandemic may also prompt some healthy companies to move in new directions.</p>
<p>Karl Schmedders: We may see in this merger and acquisition activity very strange marriages where one company depends in some form on another company and wants to keep it alive. There was a very interesting example in the United States last year, where a big department store, JC Penney, went under. And nobody wanted to buy them, so it looked like they would literally completely vanish. And then they were bought not by another retailer, they were <a href="https://www.nytimes.com/2020/09/09/business/jc-penney-sale-simon-brookfield.html">bought by real estate companies</a> owning shopping centres because they’ve wanted the store to stay in these buildings.</p>
<p>Gemma: When I asked Sandy Brian Hager about what might happen next, he said he feared that larger companies could get even richer and bigger, while smaller ones suffer even more. This is what he calls a <a href="https://www.weforum.org/agenda/2020/12/k-shaped-covid19-coronavirus-recovery/">K-shaped recovery</a>.</p>
<p>Sandy: You know, you can imagine the shape of a letter K. And what it means is that large corporations are kind of seeing their fortunes rebound. Since the pandemic first hit, they’re seeing their profitability and sales being restored. They’re seeing their financial conditions improving. Whereas smaller corporations are heading in the opposite direction.</p>
<p>Gemma: But it would be a mistake to think that this has been caused by the pandemic. Sandy says that in the US and the UK, the economy has been developing in a K-shape for some time.</p>
<p>Sandy: So if we look at, you know, the improving fortunes of large corporations that’s a process that’s been taking place since the early 1980s. And smaller corporations have been in, in a lot of financial distress for decades now.<br>
There’s this argument that’s making the rounds at the moment that suggests that, you know, the pandemic might be an opportunity of sorts in that the pandemic might actually end up killing off a lot of these zombies and that will restore dynamism to the economy. And I think that certainly could be the case. But if the pandemic ends up killing off a lot of these smaller companies, there’s no guarantee that dynamism is going to be restored. </p>
<p>Gemma: Sandy’s research shows that over the past few decades it’s smaller corporations which have been investing more of their revenues in the kinds of activities that create jobs.</p>
<p>Sandy: What we see is that smaller corporations have actually been increasing their fixed investment. And large corporations have actually been decreasing the amounts they invest in productive capacity the past few decades. </p>
<p>Gemma: Productive capacity refers to a company’s means to produce goods and services that will help it grow. </p>
<p>Sandy: Large corporations have a monopoly position, they don’t feel sort of pressures to invest in productive capacity because of that monopoly position. Whereas smaller corporations do feel that they have to expand productive capacity just to try to compete within this system and so those kinds of wishing for a lot of companies to be killed off as a way of trimming the fat – that’s not necessarily going to be a good thing.</p>
<p>Gemma: And he says, smaller companies going bankrupt or being bought out by bigger ones, that could ultimately threaten the overall health of the economy.</p>
<p>Sandy: I think if we look at the trends over the past few decades, there’s been a trend toward corporate concentration in most of the advanced economies and the consequences of that have been negative for society as a whole. So we’ve seen stagnation in terms of wages. We’ve seen a decreasing dynamism, decreasing innovation throughout the economy, decreasing productive investment as a result of concentration. And of course, we’re staring down this, um, prospect of climate breakdown as well. </p>
<p>We’re going to see more dominance from corporations at the top, particularly from the tech firms, from the pharmaceutical companies, those that have fared best out of the pandemic. I think that translates into increasing political power for these dominant corporations.</p>
<p>Gemma: Help has been forthcoming for some of these smaller businesses. In the US, the Biden administration’s US$1.9 trillion so-called American Rescue Plan, passed in early March, is targeting more government support at small businesses, particularly those in sectors most hit by the pandemic. But Sandy that says governments still need to address some of the structural issues that mean smaller companies struggle, while bigger ones thrive. </p>
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Read more:
<a href="https://theconversation.com/joe-bidens-us-1-9-trillion-stimulus-wont-be-enough-to-reignite-world-economy-on-its-own-157252">Joe Biden's US$1.9 trillion stimulus won't be enough to reignite world economy on its own</a>
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<p>Sandy: If we think in the medium term, I think one of the major issues is that governments are going to have to tackle this issue of monopoly power and corporate concentration, and that would mean restoring, maybe antitrust regulation, which has been rolled back since the 1980s. It would involve something maybe like patent reform to break up monopolies and try to spur innovation in product markets. And it would also involve, I think, corporate tax reform. And we wrote a piece earlier in The Conversation where we <a href="https://theconversation.com/biggest-companies-pay-the-least-tax-leaving-society-more-vulnerable-to-pandemic-new-research-132143">show that smaller corporations are also at a huge disadvantage</a> when it comes to corporate tax. So the rates they pay on their domestic income, relative to the rates that larger corporations pay on their domestic income, is so much higher.</p>
<p>Gemma: In the longer term, Sandy proposes using government-backed loans in a more targeted way, to help address some of the imbalances in the economy.</p>
<p>Sandy: Thinking even more longer term, I think we need to think about bolder reforms that might reassert some kind of democratic control over the economy, and that could involve establishing some sort of national investment fund or development bank where assistance and funding and financing for companies could be targeted at those businesses that are producing vital new technologies, such as, you know, green energy or alternatives to plastic or something like that. </p>
<p>Not to sound overly sort of pessimistic, about it, I just don’t see there being a good outcome unless we use this pandemic as a chance to implement really meaningful changes to the way that the business system operates.</p>
<p>Dan: As with a lot of things about this pandemic, it sounds like we’re just going to have to wait and see what happens next – and much of that depends on what governments around the world decide to do.</p>
<p>Gemma: Yep, and for those zombie companies, if interest rates start to go up and companies find they just can’t pay back their loans, or do a deal to restructure their debt, it could get pretty difficult. So watch this space. </p>
<p>Gemma: You can read more about Sandy Brian Hager’s recent research on US corporations, and Karl Schmedders’s analysis of the risk from zombie companies in their articles on The Conversation. Find the links in the show notes. </p>
<p>Dan: Coming up, we hear about a surprising – and very smelly, new conservation technique for endangered birds. </p>
<p>Gemma: But first, here’s Luthfi Dzulfikar, associate editor at The Conversation in Indonesia, with a few recommended reads. </p>
<p>Lutfhi Dzulfikar: Hi, my name is Luthfi Dzulfikar, an editor at The conversation based in Jakarta. Last week, we <a href="https://theconversation.com/mereka-yang-tidak-tercatat-rapuhnya-pondasi-pencatatan-sipil-di-indonesia-155650">published a story by researchers from Universitas Indonesia</a> and how a lot of low-income Indonesians currently do not have documents of personal identification and are excluded from national registries. </p>
<p>In Indonesia, access to around 17 different public services, including education, health insurance, sanitation and electricity requires identification such as through national IDs, household cards and birth certificates. But around 14% of children under 18 currently do not have one, with a sharp divide among groups of different income levels and between urban and rural households. Many factors contribute to the situation, but chief among them are lack of transportation infrastructure and scarcity of government presence in rural areas which make it difficult for low-income families to get in touch with civil registration offices. </p>
<p>Our second story comes from <a href="https://theconversation.com/hari-film-nasional-santri-muda-indonesia-produksi-film-untuk-lestarikan-dan-kritisi-tradisi-pesantren-158064">Nuril Huda</a> from the State Islamic University in Lampung, Sumatra, on the adoption of cinema and filmmaking practices by the Santri, traditional practitioners of Islam who are typically students that study at Islamic boarding schools. The emergence of numerous popular Islamic movies in recent years, the rise of the Santri middle-class and modernisation of the Islam boarding school system have driven the Santri to celebrate cinema through screenings, film discussions, and even festivals. </p>
<p>Based on his PhD thesis, Dr Huda observed how this adoption of cinema have not only helped the Santri preserve Islamic culture on screen, but also to criticise and question it. For instance, the views and customs within these Islamic boarding schools are traditionally dominated by male religious leaders. However, female Santris in reputable boarding schools have started to use cinema as a medium to advocate more gender-inclusive Islamic traditions. That’s it from the team in Jakarta. Stay safe, everyone. </p>
<p>Gemma: Luthfi Dzulfikar in Jakarta there.</p>
<p>Dan: OK. Onto our next story now, and we’re going into the world of bird conservation. Birds in many places are having a tough go of things and their populations are plummeting. Conservationist really struggle to protect them, but a few researchers have found a new way to use misinformation to fool predators </p>
<p>Gemma: Misinformation, so are we talking fake news here? </p>
<p>Dan: You could say fake news, although not the kind that circulates on the internet, of course. But the idea is the same: confuse predators by giving them some of their favourite info, in this case smells. The team just published a <a href="https://advances.sciencemag.org/content/7/11/eabe4164">new paper</a> testing this technique in New Zealand. I called up one of the researchers based in Sydney to find out more. </p>
<p>Catherine Price: My name’s Catherine Price. I’m a postdoctoral researcher at the University of Sydney in Australia. </p>
<p>Dan: And you study wildlife, do you not?</p>
<p>Catherine: I do. Yep. I worked in the conservation agency in New South Wales for quite a few years. And that got me very interested and I guess kind of concerned in how we protect threatened species in particular. Like, are we doing it in ways that are effective and can we improve those ways? And that led me to go back to uni and do a PhD. </p>
<p>Dan: When you were working in conservation, when you were going back to school, what motivated you to do this?</p>
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Read more:
<a href="https://theconversation.com/scientists-used-fake-news-to-stop-predators-killing-endangered-birds-and-the-result-was-remarkable-152320">Scientists used 'fake news' to stop predators killing endangered birds — and the result was remarkable</a>
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<p>Catherine: Yeah, so well in Australia and in New Zealand, a lot of birds, particularly ground nesting, birds are in decline, basically. They are constantly losing their nests and losing their chicks from predators. And in Australia, Europeans brought over a whole lot of species, things like foxes and cats and the birds that we have here, and also actually in New Zealand and other parts of the Pacific, they didn’t evolve with these predators.</p>
<p>New Zealand has this terrible problem with introduced predators cos they have no native mammals other than a bat. So their animals are just being absolutely destroyed. In Australia. I think it’s something like 95 species are threatened by foxes and cats. I think in New Zealand they’ve lost something like 57 or 60 species of birds or are either endangered or threatened. And at the moment, really all we can do is either try and kill the predator, which is obviously good if you can get rid of all of them, or fence off the birds, you know, somehow. We just kind of were thinking, we need some other techniques really. </p>
<p>Dan: I can hear it in your tone, you were just like, ugh, none of this is working.
It’s bad for the environment. It’s hard. What was the idea you guys came up with?</p>
<p>Catherine: So, most predators, in fact most animals, you know, they have to find food and they have to find it every day. And so they want to be as efficient as possible. They don’t want to waste physical effort, but they also don’t want to waste their headspace.</p>
<p>So, they use what we call rules of thumb, you know, they use clues as to what is going to work based on what’s worked for them before. And so animals use smell. It’s kind of evolved from the earliest bacteria. It’s a really reliable and useful source of information to tell an animal that food is where it should be.</p>
<p>Peter Banks, who was my PhD supervisor, he’d kind of been thinking a lot about smell and how predators use smell. And he basically just kind of came up with this crazy idea: what if we put smell everywhere and then it kind of makes it not useful for the predator?</p>
<p>In a sense it’s really simple. It’s like, well, if predators are finding their food using smell and you know, anyone who’s had a dog has watched how they’ve kind of honed in on something using smell. If they keep honing in on a smell and then there’s no food there, won’t they ignore it? Like if you kept kind of smelling someone having a barbecue next door and going next door, and there was no barbecue, eventually you’d stopped going. You would start to ignore that smell and use other information to try and find your food.</p>
<p>It’s just mucking with their minds, mucking with what information they’re using and getting them to ignore what is actually the smell of the bird. </p>
<p>Dan: OK, so you came up with this idea, but you needed to test it to see if it actually works right?</p>
<p>Catherine: Yeah, cause it’s a pretty crazy idea. And so that was basically my PhD, was testing the idea and trying to understand which aspects of it we could use. And so we were, I guess, predicting that they would initially be really interested in a new smell that they thought would be linked to food, but really quickly, if they found that it wasn’t useful, they would start to ignore it. And that’s what we found with rats in the bush around Sydney. So this was sort of the first trial to test the idea, to see if the rats would respond when they encountered a smell, but it wasn’t necessarily associated with any kind of food. It worked remarkably well.<br>
Dan: You went out and did this on a bigger scale. So can you tell me about your project out in the Mackenzie Basin?</p>
<p>Catherine: Yeah, so it was fortuitous, we were at a conference and we knew Grant Norbury, who’s the lead author of the <a href="https://advances.sciencemag.org/content/7/11/eabe4164">paper</a>, from previous work. And he’s a great guy, amazing scientist. Peter was chatting to him about the results. And he pulled together an amazing team of people from Landcare and we worked with them and set up this incredible experiment in the Mackenzie basin, which is in the middle of the South Island of New Zealand, beautiful, beautiful countryside. It’s the area where the rivers are coming off the mountains. You’ve got these huge braided river beds. Huge expanses of gravel with mountains in the background, it’s just stunning. But it’s full of ferrets and stoats and hedgehogs, they have introduced over there. There’s feral cats and there’s rats.</p>
<p>Dan: So all the baddies. </p>
<p>Catherine: All the baddies, and they have these shorebirds that come in and nest on the braided river beds, these sort of big expanses of gravel. And the nests are incredibly well camouflaged, you cannot see them at all.</p>
<p>Dan: And what kind of species of birds are we talking here? </p>
<p>Catherine: So, the main one we worked on was double-banded plovers, which are these sort of small, you know, they’re like the size of your fist kind of thing. And they lay these tiny eggs, which just look like gravel. They also have, wrybills, which are another endangered shorebird, which are very similar. And then there were also a bigger bird called the South Island oyster catcher. And all of these birds, the main cause of their decline is that the predators just come in and take the nests and they’ll lose up to 95% of their nests each year. Like it’s amazing there are any left at all really, when you look at it. </p>
<p>Dan: So walk me through: what’s step one? </p>
<p>Catherine: Grant works for Landcare, they have a team of chemists. So the first thing was, well, we’ve got to make bird odour. How do we make bird smell in the quantities that we’re going to need? And we went out and caught a couple of these birds. And tried to see if we could get the smell off them by rubbing them in towels – without hurting the birds, obviously. And basically they don’t actually smell that much from what we could pick up off a towel. So it’s like, “Jeepers, what are we going to do?” So we thought, well, what about if we could use, just chicken, quail, maybe duck or something like that? Get a whole lot of easy-to-obtain bird smells. Could we get the predators to essentially kind of generalise them all together? And so that’s, that’s what we did. We did some trials in captivity and showed that the predators did do that if they were exposed to one bird odour, they’d sort of ignore all bird odours. And so that instantly made it feasible. </p>
<p>So the chemists at Landcare were able to essentially just <a href="https://www.youtube.com/watch?v=Ac5uhBiW4MQ">boil up in a solvent chickens and quails</a>. I think these guys are normally used to doing these really fine experiments and that was stuffing whole birds into these massive kind of jugs of solvent and then mixing them up, you know, and extracting these tiny amounts of goop. But it really did smell like the bird. It was amazing. </p>
<p>Dan: So you’ve got this bird scent. Then what happens?</p>
<p>Catherine: Mix it into Vaseline. And then we had sites where we knew the birds would come and nest. And so for about a month before we knew the birds would arrive, we were walking back and forth across this landscape and dolloping bird smell every sort of 100 metres throughout this area. I mean, it was pretty labour intensive. </p>
<p>We also had cameras monitoring predator behaviour around the bird smell and monitoring the number of predators that were around. I didn’t do it the whole time. The guys that did it were so fit by the end of it. Like it was snowing at times.
It was so windy, it would rain. Yeah, they just did an amazing, incredible job.</p>
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<p>Dan: OK. So did you save the birds? Tell me the results. </p>
<p>Catherine: It did, it worked. The birds arrived. We had another team of ornithologists, so specialised bird biologists, who were monitoring the nests at both the sites where we had odour and the sites where we didn’t. And we got, it was like a 70% increase. </p>
<p>Dan: Wow. </p>
<p>Catherine: In hatching success. Yeah. Pretty much across the board of all the species. So it was pretty astounding, because we didn’t remove any predators. There was the same, pretty much the same number of predators at the control versus the treatment sites. What we noticed with the predator behaviour is when we first started putting the smell out, the predators are really interested and then that interest in the odour drops off quite quickly. And then it’s fairly low for the rest of the experiment. When the birds arrive, there’s a slight uptick in the interest, but then it drops off again. </p>
<p>Dan: That’s a huge increase, 70% increase in hatching success. So are you going to start seeing increases in populations of the birds because of this? </p>
<p>Catherine: We had some, modellers at Landcare look at that and say, well, if you did this and you got this increase each year, does it have a population-level kind of benefit? And it really does. So it basically adds about 700 birds to the population over kind of 25 years or something, I think – if you start at kind of a thousand birds. So you essentially, almost, you’re getting towards doubling the population. </p>
<p>Dan: It’s great to have this result. Do you think this might get put into practice
other places? Have people contacted you, I guess? </p>
<p>Catherine: Yeah, so we’ve had quite a bit of interest. People in Hawaii who are trying to deal with feral pigs taking birds there, because Hawaii has a big problem with invasive predators. We’ve also had people in other parts of America who are actually dealing with crabs and coyotes taking birds.</p>
<p>There’s in the UK and Europe, issues with, so foxes are native there and take shorebirds. So they don’t want to call the foxes. They’ve also got a whole lot of endangered native predators, like pine martins and wolves and things like that. So there’s a lot of potential in areas where you’ve got endangered predators that you obviously don’t want to hurt, but you’ve also got endangered birds that you’re trying to protect from them. And that’s, I guess, where we see it potentially having really big uptake.</p>
<p>Dan: Catherine, thank you so much for taking the time to speak with me today. Thank you for coming up with this, cause I can always use a good news, conservation story.</p>
<p>Catherine: Thanks. </p>
<p>Dan: If any of our listeners are conservationists and want to get in touch with Catherine Price, she was very happy to speak with anyone interested. </p>
<p>You can <a href="https://theconversation.com/scientists-used-fake-news-to-stop-predators-killing-endangered-birds-and-the-result-was-remarkable-152320">read the article she co-authored with her colleague Peter Banks</a> about their new study in the Mackenzie basin by clicking on the link in the show notes. </p>
<p>Gemma: That’s it for this week. Thanks to all the academics who’ve spoken to us for this episode – and to The Conversation editors Steven Vass, Luthfi Dzulfikar and Stephen Khan. And thanks too to Alice Mason, Imriel Morgan and Sharai White for our social media promotion. </p>
<p>Dan: You can find us on Twitter <a href="https://twitter.com/TC_Audio">@TC_Audio</a> or on Instagram at <a href="https://www.instagram.com/theconversationdotcom/?hl=en">theconversationdotcom</a> or email us at podcast@theconversation.com. </p>
<p>And if you want to learn more about any of the things we talked about on the show today, links are of course <a href="https://theconversation.com/the-zombie-company-problem-and-what-it-means-for-our-economies-podcast-158544">in the shownotes</a> and you can sign up to our <a href="https://theconversation.com/newsletter?utm_campaign=PodcastTCWeekly&utm_content=newsletter&utm_source=podcast">free daily email</a>. </p>
<p>Gemma: This episode is co-produced by Mend Mariwany and me, Gemma Ware, with sound design by Eloise Stevens. Our theme music is by Neeta Sarl. </p>
<p>Dan: And I’m Dan Merino. Thank you all and we’ll talk to you next week.</p><img src="https://counter.theconversation.com/content/158554/count.gif" alt="The Conversation" width="1" height="1" />
A transcript of episode 10 of The Conversation Weekly podcast, including a story on a new technique to prevent predators eating the eggs of endangered birds.Gemma Ware, Head of AudioDaniel Merino, Associate Breaking News Editor and Co-Host of The Conversation Weekly PodcastLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1516722021-03-01T13:16:26Z2021-03-01T13:16:26ZWhy do flowers smell?<figure><img src="https://images.theconversation.com/files/376865/original/file-20201231-17-b5tlb0.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">A floral scent can be enjoyable for a person, but it has an important job for the flower.</span> <span class="attribution"><span class="source">Richard L. Harkess</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span></figcaption></figure><figure class="align-left ">
<img alt="" src="https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=293&fit=crop&dpr=1 600w, https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=293&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=293&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=368&fit=crop&dpr=1 754w, https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=368&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=368&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
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<p><em><a href="https://theconversation.com/us/topics/curious-kids-us-74795">Curious Kids</a> is a series for children of all ages. If you have a question you’d like an expert to answer, send it to <a href="mailto:curiouskidsus@theconversation.com">curiouskidsus@theconversation.com</a>.</em></p>
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<p><strong>Why do flowers smell? – Henry E., Age 9, Somerville, Massachusetts</strong></p>
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<p>Imagine walking through a tropical forest as a sweet scent wafts through the air. A little farther down the path, the putrid stench of rotting flesh makes you catch your breath. Upon investigation, you find that both odors originate from flowers – but why do flowers smell like anything at all?</p>
<p>It’s actually part of a strategy that helps flowering plants reproduce themselves and spread their species. Certain scents help these flowers solve a big problem.</p>
<p>Plants flower to produce seeds that can go on to become new plants. To make a viable seed, pollen from one part of the flower must <a href="https://www.fs.fed.us/wildflowers/pollinators/What_is_Pollination/">fertilize the ovules</a> in another part of the flower. <a href="https://www.fs.fed.us/wildflowers/pollinators/What_is_Pollination/birdsandbees.shtml">Some plants can self-pollinate</a>, using their own pollen to fertilize the ovule. Others require pollen from another plant of the same species – that’s called <a href="https://www.fs.fed.us/wildflowers/pollinators/What_is_Pollination/birdsandbees.shtml">cross-pollination</a>.</p>
<p>So how does one plant get some other individual plant’s pollen where it needs to be?</p>
<p>Sometimes gravity helps pollen fall into place. Sometimes wind carries it. Wind-pollinated flowers, like those of many trees and grasses, don’t produce a scent.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/382302/original/file-20210203-21-1afen3g.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Bee transfers pollen from one blossom to another" src="https://images.theconversation.com/files/382302/original/file-20210203-21-1afen3g.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/382302/original/file-20210203-21-1afen3g.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=399&fit=crop&dpr=1 600w, https://images.theconversation.com/files/382302/original/file-20210203-21-1afen3g.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=399&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/382302/original/file-20210203-21-1afen3g.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=399&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/382302/original/file-20210203-21-1afen3g.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=501&fit=crop&dpr=1 754w, https://images.theconversation.com/files/382302/original/file-20210203-21-1afen3g.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=501&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/382302/original/file-20210203-21-1afen3g.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=501&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Animal pollinators can carry pollen from one flower’s stigma to another flower’s ovule as they forage for food.</span>
<span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/illustration/the-process-of-cross-pollination-with-bee-royalty-free-illustration/1060121100">ttsz/iStock via Getty Images Plus</a></span>
</figcaption>
</figure>
<p>Other flowers are pollinated by birds, bats, insects or even small rodents carrying the pollen from one flower to another. In these cases, the flowers might provide a little incentive. <a href="https://www.esa.org/blog/2018/04/04/vertebrate-polinator-metaanalysis/">Animal pollinators are rewarded</a> by sweet energy- and nutrient-rich nectar or protein-packed pollen they can eat.</p>
<p>Flowers that need the help of insects and bats go one step further, producing a floral scent that acts as a smelly kind of welcome sign for just the right pollinator.</p>
<p>An orchid blooming in the tropical forest or a rose in your garden needs to attract a pollinator to bring pollen from flowers of the same species. However, there are flowers which look similar but are from other species. To differentiate itself from other flowers, each species’ flowers puts out a unique scent to attract specific pollinators.</p>
<p>Similar to the perfumes at a department store counter, flower scents are made up from a large and diverse number of chemicals which evaporate easily and float through the air. The type of chemical, its amount and its interaction with other chemicals give the flower its unique scent. The <a href="https://www.smithsonianmag.com/smart-news/why-do-flowers-smell-good-349826/">scent of a rose</a> may consist of as many as 400 different chemicals.</p>
<p>People can smell these floral scents because they easily evaporate from the flower, drifting on the air currents to attract pollinators. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/382303/original/file-20210203-21-8gnlyv.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="corpse flower blossom in a greenhouse" src="https://images.theconversation.com/files/382303/original/file-20210203-21-8gnlyv.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/382303/original/file-20210203-21-8gnlyv.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/382303/original/file-20210203-21-8gnlyv.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/382303/original/file-20210203-21-8gnlyv.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/382303/original/file-20210203-21-8gnlyv.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/382303/original/file-20210203-21-8gnlyv.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/382303/original/file-20210203-21-8gnlyv.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=566&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">The giant corpse flower has a very stinky scent that its pollinators love.</span>
<span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/photo/titan-arum-royalty-free-image/911610946">Photography by Mangiwau/Moment via Getty Images</a></span>
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<p>Flower fragrances may be sweet and fruity, or they can be musky, even stinky or putrid depending on the pollinator they are trying to attract. A blooming apple or cherry tree emits a sweet scent to attract bumblebees, honeybees and other bees. But stick your nose into the beautiful flowers of a pear tree – a close relative of apples and cherries – and you may recoil in disgust, as these flowers smell musky or putrid to attract flies as pollinators. Similarly, the <a href="https://www.usbg.gov/corpse-flowers-us-botanic-garden">corpse flower</a>, native to Indonesian rainforests, emits a foul odor reminiscent of rotting flesh to attract flies and beetles to pollinate its flowers.</p>
<p>Moths and bats flying at night locate flowers by the scent some release after the Sun goes down. The night-blooming cereus, the saguaro cactus and the dragon fruit all have large white flowers which open at night – they seem to glow in the moonlight, making them visible to nocturnal visitors. Their strong perfume helps guide pollinators inside. While drinking the sweet nectar, the pollinator picks up pollen which it then deposits in the next flower visited.</p>
<p>Once pollinated, the flower stops producing a floral scent and nectar and redirects its energy to the fertilized embryo that will become the seed.</p>
<hr>
<p><em>Hello, curious kids! Do you have a question you’d like an expert to answer? Ask an adult to send your question to <a href="mailto:curiouskidsus@theconversation.com">CuriousKidsUS@theconversation.com</a>. Please tell us your name, age and the city where you live.</em></p>
<p><em>And since curiosity has no age limit – adults, let us know what you’re wondering, too. We won’t be able to answer every question, but we will do our best.</em></p><img src="https://counter.theconversation.com/content/151672/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Richard Harkess has received funding from USDA/NIFA. </span></em></p>Not all flowers smell good, to people at least, but their scents are a way to attract pollinators.Richard L. Harkess, Professor of Floriculture and Ornamental Horticulture, Mississippi State UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1541402021-01-29T13:25:29Z2021-01-29T13:25:29ZAnosmia, the loss of smell caused by COVID-19, doesn’t always go away quickly – but smell training may help<figure><img src="https://images.theconversation.com/files/380974/original/file-20210127-23-f1ng7j.jpg?ixlib=rb-1.1.0&rect=0%2C51%2C8647%2C5704&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">The loss of the ability to smell is known as anosmia and can result in a loss of appetite.</span> <span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/photo/hope-this-isnt-a-sign-of-the-virus-royalty-free-image/1284891263?adppopup=true">ljubaphoto/E+ via Getty Images</a></span></figcaption></figure><p><em>Editor’s note: <a href="https://scholar.google.com/citations?user=LM4rWGYAAAAJ&hl=en">Julie Walsh-Messinger</a> is a clinical psychologist who studies the effects of long-term smell loss. Her research has focused on smell loss in people with serious and persistent mental illnesses, but since the beginning of the coronavirus pandemic, she has also studied <a href="https://theconversation.com/daily-diy-sniff-checks-could-catch-many-cases-of-covid-19-150717">smell loss caused by COVID-19</a>. <a href="https://youtu.be/jjPsrHln0dA">In this interview</a>, she talks about how COVID-19 can affect your sense of smell, the effects of long-term smell loss and resources that can help.</em></p>
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<figcaption><span class="caption">Julie Walsh-Messinger talks about the effects of smell loss caused by COVID-19.</span></figcaption>
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<h2>How does COVID-19 disrupt the sense of smell?</h2>
<p>COVID-19 is not the only virus that affects our ability to smell, but it’s unique in the way in which it does so. For example, the common cold causes an inflammatory response in the nose, and that builds up mucus which reduces your ability to smell, making it a muted sense.</p>
<p>What’s unique about COVID-19 is that it actually is not nasal congestion or that nasal inflammatory response that is causing the smell loss. The virus actually <a href="https://doi.org/10.1038/s41593-020-00771-8">crosses the blood-brain barrier</a> and gets into the nervous system. It affects the nervous system and the neural connections that are necessary to detect odor and interpret it.</p>
<h2>How is this affecting people over the long term?</h2>
<p>COVID-19 affects the <a href="https://dx.doi.org/10.1177%2F1073858420956905">nervous system</a> and <a href="https://doi.org/10.1016/j.amjoto.2020.102581">sometimes</a> results in profound loss or a complete inability to smell. <a href="https://dx.doi.org/10.1016%2Fj.amjoto.2020.102725">Some people</a> recover their ability to smell within a few days or weeks, but for some people it’s been going on for much longer. Scientists are still not sure how many people lose their ability to smell completely, a condition known as anosmia.</p>
<p>This is really taking its toll on the people who have not had their sense of smell, sometimes for months, or even upwards of almost a year at this point. It can have real consequences. For example, if you can’t smell smoke, you are relying on a smoke detector to tell you there’s a fire. It is also affecting quality of life. Food doesn’t taste good anymore because <a href="https://www.scientificamerican.com/article/experts-how-does-sight-smell-affect-taste/">how you perceive taste is really a combination</a> of smell, taste and even the sense of touch. Some people are reporting weight loss due to loss of appetite, and they’re just not able to take pleasure in the things that they’ve previously found pleasurable.</p>
<h2>What are some functions of our sense of smell that we don’t often think about?</h2>
<p>Our sense of smell is really important for daily functions. There’s research that suggests that our sense of smell can influence our <a href="https://www.discovermagazine.com/mind/the-sense-of-smell-in-humans-is-more-powerful-than-we-think">attraction to certain people unconsciously</a>. It’s one of the ways in which we select mates who are less genetically similar to us, which can be an advantage for reproduction. It can also help us detect fear in others, which is important for survival. </p>
<p>It is a sense that subtly drives a lot of the decisions that we make on a daily basis but are not consciously aware of.</p>
<h2>What are some resources for people who are affected by anosmia?</h2>
<p>There are resources available to people who have smell and taste loss, though some of these aren’t just COVID-19 related. The <a href="https://gcchemosensr.org/">Global Consortium for Chemosensory Research</a> is a group of scientists who came together very quickly in the spring of 2020 to study the effects of smell and taste loss. You can participate in our research so we can learn more about what’s causing this and how to deal with it. There are <a href="https://gcchemosensr.org/patient-orgs/">links to many other resources</a> on the site.</p>
<p>There are also people and organizations doing smell training. <a href="https://theconversation.com/covid-killed-your-sense-of-smell-heres-how-experts-train-people-to-get-theirs-back-150989">Smell training</a> is essentially smelling the same odors over and over so that you can retrain your body’s ability to detect and identify that odor. We are optimistic that the sense of smell will come back for some of the people who lose their sense of smell for several months. One of the groups that is involved in smell training is the nonprofit <a href="https://abscent.org/">Abscent</a>. It wasn’t set up specifically for COVID-19 patients but has been a pioneer in smell training.</p><img src="https://counter.theconversation.com/content/154140/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Julie Walsh-Messinger does not work for, consult, own shares in or receive funding from any company or organization that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>An expert in olfaction explains the effects of long-term smell loss, the subtle role the sense plays in our lives and resources for those affected.Julie Walsh-Messinger, Assistant Professor of Psychology, University of DaytonLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1518322021-01-13T13:20:18Z2021-01-13T13:20:18ZThe scent of sickness: 5 questions answered about using dogs – and mice and ferrets – to detect disease<figure><img src="https://images.theconversation.com/files/378085/original/file-20210111-15-1b5qelp.jpg?ixlib=rb-1.1.0&rect=18%2C6%2C2026%2C1355&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Moose, a mixed-breed dog from the Nebraska Humane Society, trains in odor-detection work. </span> <span class="attribution"><span class="source">Bill Cotton/CSU</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span></figcaption></figure><p><em>Editor’s note: As COVID-19 continues to spread worldwide, scientists are analyzing new ways to track it. One promising approach is <a href="https://doi.org/10.1038/d41586-020-03149-9">training dogs to detect people who are infected</a> by smelling samples of human urine or sweat. Research scientist Glen Golden, who has trained dogs and ferrets to detect avian flu in birds, explains why certain animals are well suited to sniff out sickness.</em></p>
<h2>1. Which species have a nose for disease?</h2>
<p>Some animals have highly developed senses of smell. They include rodents; dogs and their wild relatives, like wolves and coyotes; and <a href="https://www.britannica.com/topic/list-of-mustelids-2058294">mustelids</a> – carnivorous mammals such as weasels, otters and ferrets. These species’ brains have three or more times more functional olfactory receptor neurons – nerve cells that respond to odors – than species with less keen smelling abilities, including humans and other primates. </p>
<p>These neurons are responsible for detecting and identifying volatile olfactory compounds that send meaningful signals, like smoke from a fire or the aroma of fresh meat. A substance is volatile if it changes readily from liquid to gas at low temperatures, like the acetone that gives nail polish remover its fruity smell. Once it vaporizes, it can spread rapidly through the air.</p>
<p>When one of these animals detects a meaningful odor, the chemical signal is translated into messages and transported throughout its brain. The messages go simultaneously to the olfactory cortex, which is responsible for identifying, localizing and remembering odor, and to other brain regions responsible for decision-making and emotion. So these animals can detect many chemical signals over great distances and can make rapid and accurate mental associations about them. </p>
<h2>2. How do researchers choose a target scent?</h2>
<p>In most studies that have used dogs to detect cancer, the dogs have identified physical samples, such as skin, urine or breath, from patients who either have been diagnosed with cancer or have <a href="https://doi.org/10.1016/j.applanim.2004.04.008">undiagnosed cancer at an early stage</a>. Scientists don’t know what odor cue the dogs use or whether it varies by type of cancer.</p>
<p>The U.S. Department of Agriculture’s <a href="https://www.aphis.usda.gov/aphis/ourfocus/wildlifedamage/programs/nwrc">National Wildlife Research Center</a> in Colorado and the <a href="https://monell.org/">Monell Chemical Senses Center</a> in Pennsylvania have trained mice to detect <a href="https://doi.org/10.1371/journal.pone.0075411">avian influenza in fecal samples from infected ducks</a>. Bird flu is hard to detect in wild flocks, and it <a href="https://www.cdc.gov/flu/avianflu/avian-in-humans.htm">can spread to humans</a>, so this work is designed to help wildlife biologists monitor for outbreaks. </p>
<p>The Kimball lab at Monell taught the mice to get a reward when they smelled a confirmed positive sample from an infected animal. For example, mice would get a drink of water when they traveled down the arm of a Y-shaped maze that contained feces from a duck infected with avian influenza virus. </p>
<p>By chemically analyzing the fecal samples, researchers found that the concentration of volatile chemical compounds in them changed when a duck became infected with bird flu. So they inferred that this altered smell profile was what the mice recognized.</p>
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<figcaption><span class="caption">Members of the mustelid family, such as ferrets, badgers and otters, have highly developed senses of smell. Here a wolverine sniffs out frozen meat buried deep in the snow.</span></figcaption>
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<p>Building on that work, we’ve trained ferrets and dogs to detect avian influenza in fowl, such as wild ducks and domestic chickens, in a collaborative study between Colorado State University and the National Wildlife Research Center that is currently under review for publication.</p>
<p>With ferrets, we started by training them to alert, or signal that they had detected the target odor, by scratching on a box that contained high ratios of those volatile compounds and to ignore boxes that contained low ratios. Next we showed the ferrets fecal samples from both infected and noninfected ducks, and the ferrets immediately began alerting to the box containing the fecal sample from an infected duck. </p>
<p>This approach is similar to the way that dogs are trained to detect known volatile odors in explosives or illegal drugs. Sometimes, though, we have to let the detector animal determine the odor profile that it will respond to.</p>
<h2>3. Can animals be trained to detect more than one target?</h2>
<p>Yes. To avoid confusion about what a trained animal is detecting, we can teach it a different behavioral response for each target odor. </p>
<p>For example, the dogs in the U.S. Department of Agriculture’s <a href="https://www.aphis.usda.gov/aphis/ourfocus/wildlifedamage/programs/nwrc/sa_spotlight/sniffing+out+disease">Wildlife Services Canine Disease Detection Program</a> respond with an aggressive alert, such as scratching, when they detect a sample from a duck infected with bird flu. When they detect a sample from a white-tailed deer infected by the prion that causes <a href="https://www.cdc.gov/prions/cwd/index.html">chronic wasting disease</a>, they respond with a passive alert such as sitting down.</p>
<p>Research at the University of Auburn has shown that dogs can remember and respond to <a href="https://doi.org/10.1007/s10071-020-01362-7">72 odors during an odor memory task</a>. The only limitation is how many ways a dog can communicate about different odor cues. </p>
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<a href="https://images.theconversation.com/files/378089/original/file-20210111-21-8ff0si.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Sign showing images of a dog and the SARS-CoV-2 virus." src="https://images.theconversation.com/files/378089/original/file-20210111-21-8ff0si.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/378089/original/file-20210111-21-8ff0si.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/378089/original/file-20210111-21-8ff0si.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/378089/original/file-20210111-21-8ff0si.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/378089/original/file-20210111-21-8ff0si.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=502&fit=crop&dpr=1 754w, https://images.theconversation.com/files/378089/original/file-20210111-21-8ff0si.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=502&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/378089/original/file-20210111-21-8ff0si.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=502&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
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<span class="caption">A sign notifies travelers about a pilot study at Helsinki airport that offers free coronavirus tests using dogs to detect infections by smell.</span>
<span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/news-photo/airport-signs-illustrate-the-new-covid-19-canine-test-news-photo/1228704590">Shoja Lak/Getty Images</a></span>
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<h2>4. What kinds of factors can complicate this process?</h2>
<p>First, any organization that trains animals to detect disease needs the right type of laboratory and equipment. Depending on the disease, that could include personal protection equipment and air filtering. </p>
<p>Another concern is whether the pathogen might infect the detection animals. If that’s a risk, researchers may need to inactivate the samples before they expose the animals. Then they need to see whether that process has altered the volatiles that they are teaching the animals to associate with infection. </p>
<p>Finally, handlers have to think about how to reinforce the desired response from detection animals in the field. If they are working in a population of mostly noninfected people – for example, in an airport – and an animal doesn’t get a chance to earn a reward, it may lose interest and stop working. We look for animals that have a strong drive to work without stopping, but working for a long time without reward can be challenging for even the most motivated animal. </p>
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<h2>5. Why not build a machine that can do this?</h2>
<p>Right now we don’t have devices that are as sensitive as animals with well-developed senses of smell. For example, a dog’s sense of smell is <a href="https://doi.org/10.1016/j.applanim.2005.07.009">at least 1,000 times more sensitive than any mechanical device</a>. This could explain why dogs have detected cancer in tissue samples that have been <a href="https://doi.org/10.1016/j.applanim.2004.04.008">medically cleared as not cancerous</a> </p>
<p>We also know that ferrets can detect avian flu infection in fecal samples before and after laboratory analysis shows that the virus has stopped shedding. This suggests that for some pathogens, there may be changes in volatiles in individuals who are infected but are asymptomatic. </p>
<p>As scientists learn more about how mammals’ sense of smell works, they’ll have a better chance of creating devices that are as sensitive and reliable in sniffing out disease.</p><img src="https://counter.theconversation.com/content/151832/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Glen Golden receives funding from the United Stated Department of Agriculture.</span></em></p>Scientists are experimenting with using dogs to sniff out people infected with COVID-19. But dogs aren’t the only animals with a nose for disease.Glen J. Golden, Research Scientist/Scholar I, Colorado State UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1507172020-12-09T13:17:28Z2020-12-09T13:17:28ZDaily DIY sniff checks could catch many cases of COVID-19<figure><img src="https://images.theconversation.com/files/373687/original/file-20201208-18-1ilsfhz.jpg?ixlib=rb-1.1.0&rect=1260%2C0%2C4746%2C3800&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Suddenly unable to smell your morning coffee? You likely have COVID-19.</span> <span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/photo/flat-lay-composition-cups-of-hot-coffee-and-blanket-royalty-free-image/1199773753?adppopup=true"> Kseniya Ovchinnikova/Moment via Getty Images</a></span></figcaption></figure><p>Smell loss – called anosmia – is a <a href="https://theconversation.com/covid-19-smell-and-taste-how-is-covid-19-different-from-other-respiratory-diseases-139543">common symptom of COVID-19</a>. For the past nine months, the two of us – a <a href="https://scholar.google.com/citations?hl=en&user=UGnVHZgAAAAJ">sensory scientist</a> and an <a href="https://scholar.google.com/citations?hl=en&user=QK96wxEAAAAJ">infectious disease epidemiologist</a> – have applied our respective expertise to develop smell-based screening and testing programs as part of a response to the SARS-CoV-2 pandemic. </p>
<p>In early October, one of our graduate students shared the story of her mom and her daily coffee routine. It illustrates perfectly how smell checks could be used as a screening tool for COVID-19 infection. One afternoon, our graduate student’s mom went to make her habitual cup of coffee only to discover she could not smell or taste it. She’d heard from her daughter about COVID-associated anosmia, so she next tried smelling some pine-scented cleaning spray and couldn’t smell that either. </p>
<p>Given her sudden and unexplained anosmia, our student’s mom quarantined herself and got a COVID-19 test, which came back positive. By taking her smell loss seriously, getting a rapid test and self-isolating, she created a dead end for the virus, breaking the transmission chain before the virus could spread to anyone else.</p>
<p>By some estimates, <a href="https://dx.doi.org/10.1101%2F2020.07.04.20145870">44% to 77% of people with COVID-19 lose their sense of smell</a>. But many are unaware they have lost their sense of smell until they actively try to smell something that should have an odor, <a href="https://www.iflscience.com/health-and-medicine/people-are-leaving-1star-reviews-of-scented-candles-seemingly-unaware-they-have-covid/">like scented candles</a>. This is why we are encouraging people to actively try to smell something each day. Sudden unexplained anosmia is a specific symptom of COVID-19. It can be used as a daily DIY screening tool by individuals, providing another tool in the fight to contain COVID-19.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/373689/original/file-20201208-13-1jm1wj6.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Man with a clothespin plugging his nose." src="https://images.theconversation.com/files/373689/original/file-20201208-13-1jm1wj6.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/373689/original/file-20201208-13-1jm1wj6.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/373689/original/file-20201208-13-1jm1wj6.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/373689/original/file-20201208-13-1jm1wj6.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/373689/original/file-20201208-13-1jm1wj6.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/373689/original/file-20201208-13-1jm1wj6.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/373689/original/file-20201208-13-1jm1wj6.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">COVID-19 produces an unusual type of smell loss.</span>
<span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/photo/portrait-of-man-with-clothespin-on-his-nose-royalty-free-image/835482502?adppopup=true">Fernando Trabanco Fotografía/Moment via Getty Images</a></span>
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</figure>
<h2>A smell stopper</h2>
<p>COVID-19 affects your sense of smell in a different way than a common cold does. When your nose is stuffy, odorants – the lightweight odor active molecules found in the air – are physically unable to reach the smell receptors at the top of your nasal cavity.</p>
<p>With COVID-19, loss of smell is instead caused by a signaling disruption. Research has shown that the virus attacks cells behind the bridge of the nose immediately next to olfactory neurons. These supporting cells are <a href="https://doi.org/10.1126/sciadv.abc5801">covered with many of the ACE2 receptors</a> that the virus exploits to enter cells, so they are especially vulnerable. This tissue becomes inflamed, temporarily <a href="https://doi.org/10.1016/j.neuron.2020.06.032">disrupting the ability of the olfactory neurons to signal</a> the presence of an odorant. </p>
<p>Unlike the common cold, many COVID-19 patients also <a href="https://theconversation.com/covid-19-smell-and-taste-how-is-covid-19-different-from-other-respiratory-diseases-139543">lose their sense of taste as well as chemesthesis</a> – the ability to sense the tingle of carbonation or burn of chili peppers. </p>
<h2>A very specific symptom</h2>
<p>Unexplained anosmia is normally quite rare with other viral infections, especially in the absence of congestion or nasal blockage. If someone loses their sense of smell that is a good sign of a possible COVID-19 infection. In fact, recent analyses suggest that if you had to pick just one symptom, <a href="https://dx.doi.org/10.1101%2F2020.07.22.20157263">sudden smell loss may be the single best predictor</a> of a COVID-19 diagnosis.</p>
<p>Loss of smell is very specific to COVID-19, but not everyone with SARS-CoV-2 infection reports smell loss. Critically, being able to smell things does not mean you are COVID-free. If you were able to smell your coffee this morning, that is an ambiguous result: It might mean you don’t have COVID-19, but it could also mean that you are infected with SARS-CoV-2 and simply <a href="https://doi.org/10.1093/chemse/bjaa041">didn’t lose your normal sense of smell</a>.</p>
<p>While fever checks have been widely deployed, they are <em>not</em> specific to COVID-19 – many other illnesses, like the flu or strep throat, also cause fevers. Using loss of smell as a COVID-19 test is far from perfect. But because a daily smell check is very specific, instantaneous and quite literally free, it is a highly useful screening tool. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/373710/original/file-20201208-20-phji8m.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A woman smelling a dry erase marker" src="https://images.theconversation.com/files/373710/original/file-20201208-20-phji8m.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/373710/original/file-20201208-20-phji8m.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=420&fit=crop&dpr=1 600w, https://images.theconversation.com/files/373710/original/file-20201208-20-phji8m.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=420&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/373710/original/file-20201208-20-phji8m.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=420&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/373710/original/file-20201208-20-phji8m.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=528&fit=crop&dpr=1 754w, https://images.theconversation.com/files/373710/original/file-20201208-20-phji8m.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=528&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/373710/original/file-20201208-20-phji8m.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=528&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Smell tests at home – using coffee, a marker or anything else with a strong scent – are easy and free to do.</span>
<span class="attribution"><a class="source" href="https://newsroom.ap.org/detail/VirusOutbreakGermany/87cbb3585c0d494ca4ac17cc24ef1acc/photo?Query=smell%20AND%20test&mediaType=photo&sortBy=&dateRange=Anytime&totalCount=56&currentItemNo=3">AP Photo/Martin Meissner, Pool</a></span>
</figcaption>
</figure>
<h2>Do it yourself, daily</h2>
<p>The story of our graduate student’s mom illustrates how active smell checks can catch COVID-19 cases in people with no other symptoms. At Penn State, where we work, we are putting this into action.</p>
<p>This fall, the school launched our “<a href="https://agsci.psu.edu/smellcheck">Stop. Smell. Be well.</a>” project to raise awareness of the connection between sudden smell loss and COVID-19. We even developed different “sniff cards” with a peel-and-smell panel so people could check their sense of smell with a standardized tool. </p>
<p>While such a tool is preferable for research, doing a daily smell test for public health reasons does not require a bespoke sniff card. The test could be simply sniffing your morning cup of coffee or the shampoo you use in the shower. </p>
<p>Smell checks cannot and will not catch every undiagnosed infection, since an estimated <a href="https://dx.doi.org/10.1101%2F2020.07.04.20145870">quarter to half of COVID-19 patients do not lose their sense of smell</a>. But given that DIY smell tests can be done at zero cost, the downsides of using them for screening are minimal.</p>
<h2>Screening stops spread</h2>
<p>Screening is one of the most basic tools of public health. The most critical factors for an effective COVID-19 <a href="https://dx.doi.org/10.1126/sciadv.abd5393">screening tool are frequency and speed</a>, with <a href="https://theconversation.com/rapid-screening-tests-that-prioritize-speed-over-accuracy-could-be-key-to-ending-the-coronavirus-pandemic-143882">test sensitivity being secondary</a>. </p>
<p>It is easy to check your sense of smell – who doesn’t have a bag of coffee or tea in their kitchen or a bar of soap in the bathroom? And it is fast – you know immediately if your milk went sour. Combine this with the <a href="https://dx.doi.org/10.1101%2F2020.07.22.20157263">high specificity of anosmia</a> relative to other symptoms, and we believe daily at-home smell checks can help fill the need for a rapid, cheap and specific screening tool. Tracking sudden smell loss can even be used for <a href="https://doi.org/10.1038/s41467-020-18963-y">population-level monitoring of COVID-19 cases</a> within a country or region.</p>
<p>Of course, no screening program will catch 100% of cases. It is critical for individuals to continue practicing <a href="https://theconversation.com/quarantine-bubbles-when-done-right-limit-coronavirus-risk-and-help-fight-loneliness-140134">other harm reduction behaviors</a>. Still, we encourage you to <a href="https://agsci.psu.edu/smellcheck">Stop. Smell. Be well</a>. And if you do lose your sense of smell, please self-isolate and contact a health professional.</p>
<p>[<em><a href="https://theconversation.com/us/newsletters/science-editors-picks-71/?utm_source=TCUS&utm_medium=inline-link&utm_campaign=newsletter-text&utm_content=science-corona-important">The Conversation’s most important coronavirus headlines, weekly in a new science newsletter</a>.</em>]</p><img src="https://counter.theconversation.com/content/150717/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>John E Hayes has received research funding from federal agencies (USDA, NIH), state agencies (PA Dept of Ag), and commodity groups (PA Wine Marketing Research Board, The Sugar Association). He has accepted travel expenses and speaking fees from non-profit organizations (ILSI North America), food companies (Kerry Group, Hershey Company), and the federal government (FDA). He has consulted for the federal government (FDA) and food companies (Heineken, General Mills, PepsiCo) on flavor perception. He serves as a Section Editor for the journal Physiology & Behavior. His laboratory, the Sensory Evaluation Center at Penn State, also conducts routine taste tests for industrial clients to provide experiential learning for graduate and undergraduate students. External proposals for funding of COVID-19 related research are currently pending.</span></em></p><p class="fine-print"><em><span>Cara Exten receives funding from federal (NIH) and state (PA Department of Health) agencies. She is on the Board of Directors for the AIDS Resource Alliance. External proposals for funding of COVID-19 related research are currently pending.</span></em></p>COVID-19 patients often lose their sense of smell and taste. This is rare for a viral infection. At-home smell tests could be used as a screening tool and help slow the spread of the coronavirus.John E. Hayes, Professor of Food Science, Penn StateCara Exten, Assistant Professor of Epidemiology, Penn StateLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1484842020-10-26T12:00:55Z2020-10-26T12:00:55ZYour dog’s nose knows no bounds – and neither does its love for you<figure><img src="https://images.theconversation.com/files/364859/original/file-20201021-17-11td3l0.jpg?ixlib=rb-1.1.0&rect=773%2C680%2C4437%2C3000&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Dogs have been constant companions to many during the COVID-19 pandemic.</span> <span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/photo/woman-using-a-laptop-with-her-dog-sitting-on-her-royalty-free-image/1280869184">NickyLloyd/E+ via Getty Images</a></span></figcaption></figure><p>I have discovered one positive amid the pandemic: I love working with two dogs at my feet. </p>
<p>As someone who <a href="https://scholar.google.com/citations?hl=en&user=9Ctdn8QAAAAJ">studies dog cognition</a>, I often wonder: What is Charlie learning when he stops to sniff the crisp fall air? What is Cleo thinking when she stares at me while I write? Are my dogs happy?</p>
<p>I’m not alone in finding myself suddenly spending more time with my pups and contemplating what’s on their minds. <a href="https://news.stanford.edu/2020/06/29/snapshot-new-working-home-economy/">More people in the U.S. are working from home now</a> than are working in the workplace, and many now <a href="https://www.cnbc.com/2020/03/13/people-are-working-from-home-with-pets-during-coronavirus-outbreak.html">share home offices with their canine companions</a>. What’s more, many are finding their lives enriched with the addition of a new pet, as people started <a href="https://www.washingtonpost.com/nation/2020/08/12/adoptions-dogs-coronavirus/">adopting dogs at massive rates during the pandemic</a>.</p>
<p>This uptick in dog time means <a href="https://will.illinois.edu/21stshow/story/decoding-dogs">I have been fielding questions</a> from new and experienced dog owners alike about their companions’ mentalities. Many questions center on the same themes I ponder: What is my dog thinking? Am I doing everything I can to ensure my pup is content?</p>
<p>Fortunately, research on dog cognition can <a href="https://www.audible.com/pd/Decoding-Dogs-Inside-the-Canine-Mind-Audiobook/B08FXRKSK3">help unravel what is on their minds</a> and provide insight into what they need for psychologically fulfilling and happy lives.</p>
<h2>Smelling superstars</h2>
<p>Dogs are both familiar and yet fascinatingly alien. To appreciate their “otherness” all you need to do is consider their sensory world. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/364860/original/file-20201021-23-zeezzs.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A close up shot of a shaggy dog smelling the ground and looking at camera." src="https://images.theconversation.com/files/364860/original/file-20201021-23-zeezzs.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/364860/original/file-20201021-23-zeezzs.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/364860/original/file-20201021-23-zeezzs.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/364860/original/file-20201021-23-zeezzs.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/364860/original/file-20201021-23-zeezzs.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/364860/original/file-20201021-23-zeezzs.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/364860/original/file-20201021-23-zeezzs.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">A dog’s nose dominates its face for good reason.</span>
<span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/photo/dog-smelling-the-ground-and-looking-at-camera-royalty-free-image/1184184071">Capuski/iStock via Getty Images Plus</a></span>
</figcaption>
</figure>
<p>My dogs and I have very different experiences when we walk a trail. I marvel at the beautiful autumn day, but my dogs have their heads to the ground, seemingly ignoring the wonders around them. </p>
<p>However, they are appreciating something I can’t perceive: the scent of the fox who scampered through last night, the lingering odor of the dogs who’ve walked this way and the footsteps of my neighbor, who last wore her hiking shoes in woods my dogs have never visited.</p>
<p>You’ve probably heard about dogs who <a href="https://www.akc.org/expert-advice/news/meet-americas-cancer-sniffing-canines/">sniff out cancer</a>, <a href="https://www.dhs.gov/explosive-detection-canine-teams">weapons</a> <a href="https://time.com/5898049/covid-19-sniffing-dogs/">or even coronavirus</a>. These dogs are not special in their nose power: Your dog could do the same thing. In fact, the <a href="https://doi.org/10.1016/S0140-6736(89)92257-5">first dog to sniff out cancer</a> sniffed a mole on his owner’s leg so frequently that she went to the dermatologist, where she was diagnosed with melanoma.</p>
<p>A dog’s sense of smell is <a href="https://doi.org/10.1016/j.applanim.2005.07.009">estimated to be 10,000 to 100,000 times better than that of a human</a>. This is due, in large part, to staggering differences in odor processing in humans and dogs. </p>
<p>While we have about 6 million olfactory receptors, <a href="https://www.simonandschuster.com/books/Being-a-Dog/Alexandra-Horowitz/9781476796024">dogs have a staggering 300 million</a>. Their epithelium, or <a href="https://www.scribd.com/book/267676942/K9-Scent-Training-A-Manual-for-Training-Your-Identification-Tracking-and-Detection-Dog">nasal tissue, is about 30 times larger than ours</a>. And while people have between 12 million and 40 million olfactory neurons – specialized cells involved in transmitting odor information to the brain – dogs, depending on the breed, <a href="https://archive.org/details/themagicofthesenses">can have 220 million to 2 billion</a>! </p>
<p>How can you even conceptualize this breathtaking difference in abilities? This disparity is like <a href="https://www.simonandschuster.com/books/Being-a-Dog/Alexandra-Horowitz/9781476796024">detecting one teaspoon of sugar</a> in enough water to fill two Olympic sized swimming pools. </p>
<p>Now that your mind has been blown about your dog’s incredible sense of smell, you can use this information to make your dog happier by taking it on the occasional “<a href="https://www.patriciamcconnell.com/theotherendoftheleash/take-your-dog-on-a-sniff">sniffy walk</a>” – letting it lead the way and take as much time to smell as it would like. <a href="https://doi.org/10.3389/fvets.2015.00069">Such walks can make dogs happier</a> by allowing them to gain lots of information about the world around them.</p>
<h2>The love is mutual</h2>
<p>While there are parts of a dog’s mind that are alien, there are also parts that feel very familiar. Chances are, your dog occupies a special place in your heart. Recent research suggests your dog feels the same way about you. <a href="https://www.clivewynne.com/book-1">Your dog adores you</a>.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/364861/original/file-20201021-21-fgv78r.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A golden retriever type dog looks up adordingly at its owner." src="https://images.theconversation.com/files/364861/original/file-20201021-21-fgv78r.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/364861/original/file-20201021-21-fgv78r.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=399&fit=crop&dpr=1 600w, https://images.theconversation.com/files/364861/original/file-20201021-21-fgv78r.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=399&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/364861/original/file-20201021-21-fgv78r.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=399&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/364861/original/file-20201021-21-fgv78r.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=502&fit=crop&dpr=1 754w, https://images.theconversation.com/files/364861/original/file-20201021-21-fgv78r.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=502&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/364861/original/file-20201021-21-fgv78r.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=502&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">The average dog spends a lot of time gazing at its owner – creating a ‘love-loop.’</span>
<span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/photo/close-up-of-woman-with-dog-royalty-free-image/697631131">Murat Natan/EyeEm via Getty Images</a></span>
</figcaption>
</figure>
<p>Dogs attach to their owners in much the <a href="https://doi.org/10.1037/0735-7036.112.3.219">same way human infants attach to their parents</a>. Like babies, dogs show distress when left with a stranger and rush to reunite upon their person’s return. </p>
<p>A recent study found that dogs that have been deprived of food and owners <a href="https://www.hmhbooks.com/shop/books/dog-is-love/9780358414230">choose to greet their owners before eating</a>. Further, their brain’s <a href="https://www.nytimes.com/2017/09/08/science/gregory-berns-dogs-brains.html">reward centers “light up” upon smelling their owners</a>. And, when your eyes meet your dog’s, <a href="https://doi.org/10.1126/science.1261022">both your brains release oxytocin</a>, also know as the “cuddle hormone.” </p>
<p>[<em>Deep knowledge, daily.</em> <a href="https://theconversation.com/us/newsletters/the-daily-3?utm_source=TCUS&utm_medium=inline-link&utm_campaign=newsletter-text&utm_content=deepknowledge">Sign up for The Conversation’s newsletter</a>.]</p>
<p>All of this research shows that you can make your dog happier with just one ingredient: you. Make more eye contact to release that cuddle hormone. Touch it more – <a href="https://doi.org/10.1101/062703">dogs like pats better than treats</a>! Go ahead and “baby talk” to your dog – <a href="https://doi.org/10.1038/s41598-017-04671-z">it draws the dog’s attention to you more</a> and <a href="https://www.bbc.com/news/uk-43315466#:%7E:text=Using%20%22dog%2Dspeak%22%20is,University%20of%20York%20have%20found.&text=PhD%20student%20Alex%20Benjamin%20said,who%20used%20a%20high%20pitch">may strengthen your bond</a>.</p>
<p>Understanding your dog’s mind can not only sate your curiosity about your companion, but can also help you ensure your pup lives a good, happy life. The more you know about your furry friends the more you can do to meet their needs. </p>
<p>And now I am off to gaze into Cleo’s bright blue eyes, give Charlie a belly rub, and then let them take me on a “sniffy” walk.</p><img src="https://counter.theconversation.com/content/148484/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Ellen Furlong has written for Audible / The Great Courses. She has received funding from The National Institute of Health. She is a member of The Animal Behavior Society, The Comparative Cognition Society, The American Psychological Association, and The Society for Teaching of Psychology. </span></em></p>Dogs process the sensory world very differently than humans, but love in a way that is entirely familiar.Ellen Furlong, Associate Professor of Psychology, Illinois Wesleyan UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1414042020-08-06T10:17:05Z2020-08-06T10:17:05ZFour reasons why some people become ‘super smellers’ – from pregnancy to genetic differences<figure><img src="https://images.theconversation.com/files/351273/original/file-20200805-24-z254sc.jpg?ixlib=rb-1.1.0&rect=0%2C0%2C7940%2C5304&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Some super smellers even associate unpleasant memories or feelings of annoyance with certain smells. </span> <span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/young-african-american-woman-wearing-denim-1477639214">Shift Drive/ Shutterstock</a></span></figcaption></figure><p>Do certain smells make you feel uncomfortable, even nauseous? Or is your nose so good that you can detect even the subtlest aromas in your favourite wine? Perhaps certain smells evoke negative or positive feelings? If you answered yes to any of these questions, you might just be a “super smeller”.</p>
<p>Medically known as <a href="https://www.sciencedirect.com/topics/neuroscience/hyperosmia">hyperosmia</a>, super smellers are people who have a heightened sense of smell compared to the average person. Some super smellers may be more sensitive to pleasant smells, while others may be more affected by unpleasant odours. </p>
<p>Hyperosmia is <a href="https://www.sciencedirect.com/topics/neuroscience/hyperosmia#:%7E:text=Hyperosmia%20(heightened%20smell%20function)%20is,below%20those%20of%20normal%20subjects">relatively rare</a>, so there’s still much that researchers don’t know about the condition. However, here are some of the reasons a person may have hyperosmia.</p>
<h2>1. Health conditions</h2>
<p>A number of studies have reported links between various medical conditions and hyperosmia, including <a href="https://pubmed.ncbi.nlm.nih.gov/25098475/">Lyme Disease</a>, <a href="https://link.springer.com/article/10.1007/BF00313864">migraines</a>, <a href="https://pubmed.ncbi.nlm.nih.gov/11186713/">body fluid</a> <a href="https://pubmed.ncbi.nlm.nih.gov/6442085/">disturbances</a>, <a href="https://www.sciencedirect.com/science/article/abs/pii/S0163834312002186">hormone deficiency</a> and <a href="https://link.springer.com/article/10.2165/00003495-198020020-00006">certain</a> <a href="https://www.ncbi.nlm.nih.gov/pubmed/32106138">medications</a>. Though it’s not fully understood what leads to hyperosmia in these cases, it could possibly be the effect these diseases have on the body’s electrolytes, thus affecting the signals generated at the scent receptors.</p>
<p>Studies have also shown that certain <a href="https://link.springer.com/article/10.1007/s13353-014-0252-7">genetic conditions</a> such as duplication or overexpression of the <a href="https://www.sciencedirect.com/topics/biochemistry-genetics-and-molecular-biology/kal1-gene">KAL1 gene</a> – which produces a protein (anosmin-1) that appears to control the growth and movement of nerve cells that help process smell – and other genetic <a href="https://onlinelibrary.wiley.com/doi/abs/10.1002/ejp.1272">mutations</a> are linked to heightened sense of smell. </p>
<p>One study even showed that the genetic coding for a certain protein that helps to <a href="https://www.ncbi.nlm.nih.gov/pubmed/25480730">bind on to smells</a> and help them reach the smell receptors in the nose, does vary in a population, so some people may naturally have a better sense of smell than others.</p>
<h2>2. Pregnancy</h2>
<p>Many women who become pregnant often claim certain smells which never used to bother them suddenly become revolting. And one review has actually confirmed that some pregnant women do temporarily become super smellers. </p>
<p>By comparing the findings of more than 50 studies into how pregnancy alters sense of smell, researchers concluded that although pregnant women didn’t have higher smell intensity overall, they were possibly <a href="https://www.frontiersin.org/articles/10.3389/fpsyg.2014.00067/full7">more sensitive to certain odours</a>. But there wasn’t enough evidence to determine if their ability to identify more odours in general had increased.</p>
<figure class="align-center ">
<img alt="Man eating food on bed while pregnant women covers nose." src="https://images.theconversation.com/files/351274/original/file-20200805-290-9rjse0.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/351274/original/file-20200805-290-9rjse0.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=406&fit=crop&dpr=1 600w, https://images.theconversation.com/files/351274/original/file-20200805-290-9rjse0.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=406&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/351274/original/file-20200805-290-9rjse0.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=406&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/351274/original/file-20200805-290-9rjse0.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=511&fit=crop&dpr=1 754w, https://images.theconversation.com/files/351274/original/file-20200805-290-9rjse0.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=511&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/351274/original/file-20200805-290-9rjse0.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=511&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Typically, these ‘super smelling’ abilities are only temporary.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/heightened-sense-smell-during-pregnancy-pregnant-1583458078">Prostock-studio/ Shutterstock</a></span>
</figcaption>
</figure>
<p>Despite being such a commonly reported phenomenon, researchers still aren’t entirely sure why this happens. However, this sensitivity is typically temporary, rather than a permanent change.</p>
<h2>3. Brain differences</h2>
<p>A 2019 study aimed to uncover whether the brains of super smellers worked differently than normal. Researchers compared 25 men who <a href="https://link.springer.com/article/10.1007/s11682-018-0008-9">considered themselves super smellers</a> with 20 men who rated their sense of smells as normal. Using brain scans, the researchers compared the grey matter volume in parts of the brain associated with smell.</p>
<p>They found that in super smellers there was increased brain activity in two key areas responsible for bringing together smell information, and learning and memorising smells. But while research detected these brain differences, the researchers were unable to ascertain whether this was caused by genetics, or if it was learned. </p>
<p>It is well established that smell and memory are strongly linked. But the findings of a 2014 study suggest that this may be the <a href="https://journals.sagepub.com/doi/10.1177/1359105313481080">basis for hyperosmia</a>. The study looked at 55 volunteers who rated their sense of smell as better than average. They compared them to a group of people the same ages and gender who considered their sense of smell to be normal.</p>
<p>The super smellers in this study were asked to complete a structured questionnaire about their experiences of environmental smells. They associated certain smells such as fragrances and human body products (such as sweat) with negative consequences and unpleasant memories, and found that environmental smells evoked feelings of annoyance and disgust. But the study didn’t investigate whether participants were also sensitive to other smells, so it’s difficult to know if these volunteers actually had a normal or heightened sense of smell.</p>
<p>Other studies have similarly found that sensitivity to certain smells, including <a href="https://www.ncbi.nlm.nih.gov/pubmed/27221295">phenolic resins</a> (such as formaldehyde) and the shellfish-like pyridine odour in <a href="https://academic.oup.com/occmed/article-abstract/56/1/51/1374604">organic chemicals</a>, are linked with negative experiences, suggesting that sensitivity to these smells develops based on negative experiences in the workplace – for example being exposed to chemical odours at work.</p>
<h2>4. Training</h2>
<p>So does being a super smeller convey a super power that lasts continuously, or can it be temporary? </p>
<p>In 2003, I conducted a study with 230 volunteers to test their <a href="https://www.cambridge.org/core/journals/journal-of-laryngology-and-otology/article/superosmic-phenomenon/4D0D83E5A49D994EC6E3C6FD19AC17AE">depth of smell</a> for the smell of phenylethyl alcohol (the smell of roses) or eucalyptol (a mint-like smell). The depth of smell relates to how small a concentration of an odour can be detected (known as the “threshold”). We used a custom-built device that delivered eight concentrations of the smells, from barely detectable to very strong. </p>
<p>We found that 2% of the group demonstrated what we dubbed as “the superosmic phenomenon” on single testing. A further 10% demonstrated this phenomenon on various occasions during repeated testing (where the test was performed ten times on separate occasions at one-week intervals). This phenomenon occurred when the volunteers were able to detect the smells at three or more levels below where they would normally detect it – and they were able to continue detecting the smells at least ten times during the test. The test was performed once a week over a period of ten weeks.</p>
<p>In almost all cases where the superosmia occurred, this was followed by a sudden, rapid loss of smell detection at this lower level before the end of the test. So without any explanation for why, we could see evidence of short-term super smellers when focused on certain smells.</p>
<p>Overall, the assumption all super smellers achieve their “superpower” because of their genes or a rare medical condition is probably unlikely. Think about sommeliers or perfumers – these people train their noses to be able to recognise many unique smells. In fact, smell training can even allow people who have suffered smell loss to recover their <a href="http://www.fifthsense.org.uk">sense of smell</a>.</p>
<p>It seems that super smellers are a mixture of people who may be genetically wired to smell better, some who train to smell better and some who have an underlying medical condition. And others, perhaps including pregnant women, they may only experience smell sensitivity – not true hyperosmia.</p><img src="https://counter.theconversation.com/content/141404/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Carl Philpott receives funding from the National Institute of Health Research. He is affiliated with Fifth Sense. </span></em></p>Hyperosmia is relatively rare, but there are many reasons a person might develop this condition – even temporarily.Carl Philpott, Professor of Rhinology and Olfactology, University of East AngliaLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1414372020-07-08T12:13:26Z2020-07-08T12:13:26ZSynthetic odors created by activating brain cells help neuroscientists understand how smell works<figure><img src="https://images.theconversation.com/files/346129/original/file-20200707-194405-awzgsl.jpg?ixlib=rb-1.1.0&rect=767%2C8%2C4838%2C3242&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">When you sniff a particular scent, your brain cells fire in a recognizable pattern.</span> <span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/photo/young-woman-smelling-perfume-from-bottle-at-royalty-free-image/953961844">Maskot via Getty Images</a></span></figcaption></figure><p>When you experience something with your senses, it evokes complex patterns of activity in your brain. One important goal in neuroscience is to decipher how these neural patterns drive the sensory experience.</p>
<p>For example, can the smell of chocolate be represented by a single brain cell, groups of cells firing all at the same time or cells firing in some precise symphony? The answers to these questions will lead to a broader understanding of how our brains represent the external world. They also have implications for treating disorders where the brain fails in representing the external world: for example, in the loss of sight of smell.</p>
<p>To understand how the brain drives sensory experience, <a href="https://rinberglab.com">my colleagues and I</a> focus on the sense of smell in mice. We directly control a mouse’s neural activity, <a href="https://doi.org/10.1126/science.aba2357">generating “synthetic smells”</a> in the olfactory part of its brain in order to learn more about how the sense of smell works.</p>
<p>Our latest experiments discovered that scents are represented by very specific patterns of activity in the brain. Like the notes of a melody, the cells fire in a unique sequence with particular timing to represent the sensation of smelling a unique odor.</p>
<h2>Scents produced by light projections</h2>
<p>Using mice to study smell is appealing to researchers because the <a href="https://doi.org/10.1016/j.conb.2018.04.008">relevant brain circuits have been mapped out</a>, and modern tools allow us to directly manipulate these brain connections.</p>
<p>The mice we use are genetically engineered so we can activate individual brain cells simply by shining light of specific wavelengths onto them – <a href="https://doi.org/10.1038/nn1525">a technique known as optogenetics</a>. Early uses of optogenetics involved light delivered through implanted optical fibers, letting researchers control coarse patches of brain cells. More recent uses of optogenetics allow <a href="https://doi.org/10.1126/science.aaw5202">more sophisticated control</a> of <a href="https://doi.org/10.1016/j.cell.2019.05.045">precise patterns of brain activity</a>.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/346080/original/file-20200707-22-1rfavl2.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/346080/original/file-20200707-22-1rfavl2.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/346080/original/file-20200707-22-1rfavl2.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=393&fit=crop&dpr=1 600w, https://images.theconversation.com/files/346080/original/file-20200707-22-1rfavl2.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=393&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/346080/original/file-20200707-22-1rfavl2.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=393&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/346080/original/file-20200707-22-1rfavl2.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=494&fit=crop&dpr=1 754w, https://images.theconversation.com/files/346080/original/file-20200707-22-1rfavl2.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=494&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/346080/original/file-20200707-22-1rfavl2.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=494&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">A simplified image of a mouse brain, looking down from the top. The olfactory bulb (left) is at the front of the brain and receives connections from receptor cells in the nose.</span>
<span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/File:Mouse_brain_top_view.png">Database Center for Life Science/Wikimedia Commons</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
</figcaption>
</figure>
<p>For our study, we projected light patterns onto the surface of the brain, targeting a region known as the olfactory bulb. Previous research has found that when mice sniff different scents, cells in the olfactory bulb appear to fire in a sort of patterned symphony, with a <a href="https://doi.org/10.1152/jn.90902.2008">unique pattern formed in response to each distinct smell</a>.</p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/346101/original/file-20200707-194405-1ojhb4o.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/346101/original/file-20200707-194405-1ojhb4o.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/346101/original/file-20200707-194405-1ojhb4o.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=617&fit=crop&dpr=1 600w, https://images.theconversation.com/files/346101/original/file-20200707-194405-1ojhb4o.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=617&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/346101/original/file-20200707-194405-1ojhb4o.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=617&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/346101/original/file-20200707-194405-1ojhb4o.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=776&fit=crop&dpr=1 754w, https://images.theconversation.com/files/346101/original/file-20200707-194405-1ojhb4o.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=776&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/346101/original/file-20200707-194405-1ojhb4o.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=776&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Rather than receiving sensory signals from the nose, the olfactory bulb was activated by light projections.</span>
<span class="attribution"><span class="source">Edmund Chong</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<p>When we shined light patterns onto a mouse’s olfactory bulb, it generated corresponding patterns of cellular activity. We called these patterns “synthetic smells.” As opposed to a pattern of activity triggered by a mouse sniffing a real odor, we directly triggered the neural activity of a “synthetic smell” with our light projections.</p>
<p>Next we trained each individual mouse to recognize a randomly generated synthetic smell. Since they can’t describe to us in words what they’re perceiving, we rewarded each mouse with water if it licked a water spout whenever it detected its assigned smell. Over weeks of training, mice learned to lick when their assigned smell was activated, and not to lick for other randomly generated synthetic smells. </p>
<p>[<em><a href="https://theconversation.com/us/newsletters/the-daily-3?utm_source=TCUS&utm_medium=inline-link&utm_campaign=newsletter-text&utm_content=experts">Expertise in your inbox. Sign up for The Conversation’s newsletter and get expert takes on today’s news, every day.</a></em>]</p>
<p>We cannot say for sure that these synthetic smells correspond to any known odor in the world, nor do we know what they smell like to the mouse. But we did calibrate our synthetic patterns to broadly resemble olfactory bulb patterns observed when actual scents are present. Furthermore, mice learn to discriminate synthetic smells about as quickly as they did real smells.</p>
<h2>Tweaking the pattern of a synthetic smell</h2>
<p>Once each mouse learned to recognize its assigned synthetic smell, we measured how much they still licked when we modified the assigned smell. Within each synthetic pattern, we altered which cells were activated or when they activated.</p>
<p>Imagine taking a familiar song, changing individual notes in the song, and asking whether you still recognized the song after each change. By testing many different changes, one can eventually understand which precise composition of notes is essential to the song’s identity and which tweaks are extreme enough to make the song unrecognizable.</p>
<p>Likewise, by measuring how mice changed their licking as we modified their projected light patterns, we were able to understand which combinations of cells within the pattern were important for identifying the synthetic smell.</p>
<p>The precise combination of cells activated was crucial. But just as important was when they are activated in an ordered sequence, akin to timed notes in a melody. For example, changing the order of cells in the sequence would render the smell unrecognizable.</p>
<p>It turned out that the cells activated earlier in the sequence were more important for recognition – changing the sequences later in the pattern seemed to have negligible effects.</p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/lJ2bof_fWgM?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">Watch an animation of how these sequences in the brain work.</span></figcaption>
</figure>
<p>Changes in recognition were graded, and not drastic: When we changed small parts of the pattern, the smell did not become completely unrecognizable. In fact, the degree to which the smell was recognized was proportional to the degree of change in the pattern. This implies that if I slightly modify the brain activity that represents an orange, you would still smell something similar – maybe recognizing it as citrus, or fruity.</p>
<p>So while the brain has huge capacity to store many different smells in unique timed sequences of cell activity, you can still recognize similar smells by the similarity in their patterns: The smell of coffee is still distinctly recognizable even with a splash of vanilla added to it. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/346134/original/file-20200707-194418-1oc455r.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/346134/original/file-20200707-194418-1oc455r.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/346134/original/file-20200707-194418-1oc455r.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=402&fit=crop&dpr=1 600w, https://images.theconversation.com/files/346134/original/file-20200707-194418-1oc455r.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=402&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/346134/original/file-20200707-194418-1oc455r.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=402&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/346134/original/file-20200707-194418-1oc455r.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=506&fit=crop&dpr=1 754w, https://images.theconversation.com/files/346134/original/file-20200707-194418-1oc455r.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=506&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/346134/original/file-20200707-194418-1oc455r.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=506&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">You know the smell of coffee even if it’s served with a dash of fragrant vanilla.</span>
<span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/photo/hot-espresso-royalty-free-image/981402468">Roland Beerli/500px Prime via Getty Images</a></span>
</figcaption>
</figure>
<p>The next step in this research is to bring the synthetic approach to real smells. To do so, we would need to record brain activity in response to a real smell, then reactivate the very same cells using optogenetics. The synthetic re-creation of real objects in the brain is the current focus of research in <a href="https://doi.org/10.1126/science.aaw5202">multiple</a> <a href="https://doi.org/10.1016/j.cell.2019.05.045">labs</a> <a href="https://doi.org/10.1364/BRAIN.2019.BM3A.2">including ours</a>.</p>
<p>Addressing this issue is exciting because it opens up possibilities not just for understanding how the brain works, but also for developing brain implants that may one day restore the loss of sensory experiences.</p><img src="https://counter.theconversation.com/content/141437/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Edmund Chong does not work for, consult, own shares in or receive funding from any company or organization that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>Brains recognize a smell based on which cells fire, in what order – the same way you recognize a song based on its pattern of notes. How much can you change the ‘tune’ and still know the smell?Edmund Chong, Ph.D. Student in Neuroscience, New York UniversityLicensed as Creative Commons – attribution, no derivatives.