tag:theconversation.com,2011:/au/topics/face-blindness-26669/articlesFace blindness – The Conversation2016-12-13T14:18:06Ztag:theconversation.com,2011:article/696852016-12-13T14:18:06Z2016-12-13T14:18:06ZThe trouble with facial recognition technology (in the real world)<figure><img src="https://images.theconversation.com/files/149104/original/image-20161207-18049-1o8q02m.png?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">A face in a crowd in Mission: Impossible Rogue Nation.</span> <span class="attribution"><span class="license">Author provided</span></span></figcaption></figure><p>If you’ve watched any sort of spy thriller or action film over the last few years – think <a href="http://www.imdb.com/title/tt4196776/?ref_=nv_sr_1">Jason Bourne</a> or <a href="http://www.imdb.com/title/tt2381249/?ref_=nv_sr_1">Mission: Impossible</a> – the chances are you’ve seen facial recognition software in action. These movie scenes often involve an artist’s sketch compared to mug shots, or sometimes even a live CCTV stream, and with the clock ticking, a match is usually found for the culprit in the nick of time.</p>
<p>It seems natural then to assume that what happens in the film world is similar to what happens (most of the time) in the real world. We might think that our faces are constantly being tracked and recognised as we walk past security cameras in city centres – but this is not actually the case.</p>
<p>Not only would such a system require millions of cameras capable of producing high-quality footage, but it would also require the integration of photo-ID databases such as mugshots from every police force, previous passport images, and driving license images for everyone in the country. </p>
<p>And yet even if this high level of integration was possible, a far more basic problem still exists – facial recognition systems are still <a href="http://www.washington.edu/news/2016/06/23/how-well-do-facial-recognition-algorithms-cope-with-a-million-strangers/">not 100% accurate</a>.</p>
<h2>Humans on top</h2>
<p>In relatively easy situations, where faces are front-on and reasonably clear, computer algorithms can now <a href="http://www.sciencedirect.com/science/article/pii/S0262885613001741">outperform humans</a>. But in much harder conditions when faces are pictured from different angles or in poor lighting, humans still come out <a href="https://utdallas.influuent.utsystem.edu/en/publications/human-and-algorithm-performance-on-the-pasc-face-recognition-chal">on top</a>. </p>
<p>A lot of this is because of how these types of systems work in a real-world setting. Generally a computer face recognition system will provide a “candidate list” of best guesses, and from this list a human operator makes the final decision. But because these lists tend to produce several very suitable lookalikes as the target, the operator’s choice is a tough job – with error rates <a href="http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0139827">as high as 50%</a>.</p>
<p>For similar security systems, such as the <a href="http://icinspector.independent.gov.uk/wp-content/uploads/2012/02/Inspection-of-Gatwick-Airport-North-Terminal.pdf">eGates</a> used in several airports, information on their accuracy is unavailable. But there have been several cases of people being successfully “cleared” while using their <a href="http://www.dailymail.co.uk/travel/article-1357913/Security-breach-caused-new-biometric-technology-Manchester-Airport.html">partner’s passport</a> – which could well be a cause for concern.</p>
<h2>Face in a crowd</h2>
<p>When it comes to recognising a face, <a href="https://www.ncbi.nlm.nih.gov/pubmed/11676099">research shows</a> people are near perfect when shown familiar faces but fare much worse when the faces are unfamiliar. </p>
<p>It seems, the difficulty arises from the enormous amount of variability we see across different images of the same person. So even minor changes – like the addition of a <a href="http://onlinelibrary.wiley.com/doi/10.1002/acp.3261/full">pair of glasses</a> – can make us significantly worse. And most people seem to be unaware of their <a href="https://www.ncbi.nlm.nih.gov/pubmed/25988915">drop in performance</a>. </p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/149116/original/image-20161207-18059-1icj5f.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/149116/original/image-20161207-18059-1icj5f.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=264&fit=crop&dpr=1 600w, https://images.theconversation.com/files/149116/original/image-20161207-18059-1icj5f.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=264&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/149116/original/image-20161207-18059-1icj5f.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=264&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/149116/original/image-20161207-18059-1icj5f.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=332&fit=crop&dpr=1 754w, https://images.theconversation.com/files/149116/original/image-20161207-18059-1icj5f.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=332&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/149116/original/image-20161207-18059-1icj5f.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=332&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Does the middle ID image belong to the person on the left or the right? (Answer: all three are the same person).</span>
</figcaption>
</figure>
<p>In general, <a href="http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0103510">passport officers</a> are <a href="https://theconversation.com/passport-staff-miss-one-in-seven-fake-id-checks-30606">no better than university students</a> when matching <a href="http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0103510">unfamiliar people</a> – and research shows that <a href="https://www.ncbi.nlm.nih.gov/pubmed/24919354">training</a> in this area doesn’t seem to make a difference – you’ve either got it or you haven’t. </p>
<p>But there are also large individual differences in abilities over the population – from those who are clinically “<a href="https://theconversation.com/i-should-know-you-face-blindness-and-the-problem-of-identifying-others-8884">face blind</a>” to the highly accurate “<a href="http://superrecognisers.com/">super recognisers</a>” – who are able to do just that, be super at recognising.</p>
<h2>Faces of the future</h2>
<p>Looking to the future, for automatic face recognition systems there is increasing evidence that using “face averages” may improve identification rates. These averages are computer-generated images, made by combining several photographs of the same person. </p>
<p>Computer algorithms <a href="http://science.sciencemag.org/content/319/5862/435">show an advantage</a> when using these averages to compare to a target image. A <a href="http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0119460">simple smartphone system</a> is also better at recognising a user if an average image is stored in its memory.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/149119/original/image-20161207-18036-5ffcf8.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/149119/original/image-20161207-18036-5ffcf8.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=248&fit=crop&dpr=1 600w, https://images.theconversation.com/files/149119/original/image-20161207-18036-5ffcf8.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=248&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/149119/original/image-20161207-18036-5ffcf8.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=248&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/149119/original/image-20161207-18036-5ffcf8.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=312&fit=crop&dpr=1 754w, https://images.theconversation.com/files/149119/original/image-20161207-18036-5ffcf8.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=312&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/149119/original/image-20161207-18036-5ffcf8.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=312&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Catching criminals in the new Jason Bourne film is still more fiction than fact.</span>
<span class="attribution"><span class="source">Screenshot</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>But it may well be that long-term, we choose to leave behind our belief that facial comparison is the solution – and instead embrace other means of identification. </p>
<p>This could include iris and retinal scans, fingerprints, and even signature matching – all of which are considered to be <a href="http://www.sciencedirect.com/science/article/pii/S0165168403002019">more accurate</a> than using faces. </p>
<p>So as things currently stand, there’s no need to be concerned about being recognised by cameras as you walk down the high street just yet. Because for the time being, you’re still just a face in a crowd.</p><img src="https://counter.theconversation.com/content/69685/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Kay Ritchie has received funding from the Australian Department of Education (Endeavour Research Fellowship). </span></em></p><p class="fine-print"><em><span>Robin Kramer 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>Big brother is not watching you … yet.Robin Kramer, Postdoctoral Research Fellow in the Department of Psychology, University of YorkKay Ritchie, Lecturer in Cognitive Psychology, University of LincolnLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/672112016-11-09T10:19:15Z2016-11-09T10:19:15ZCan you teach recognition to the face-blind?<figure><img src="https://images.theconversation.com/files/145028/original/image-20161108-16685-1pzupa0.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Sorry, but you are...?</span> <span class="attribution"><a class="source" href="http://www.shutterstock.com/pic-213490135/stock-photo-businessman-with-paper-bag-on-the-head-in-the-street.html?src=e1UoWybw8LJb-Z53OcAMig-6-70">Tomas Urbelionis/www.shutterstock.com</a></span></figcaption></figure><p>Every day, we often scan hundreds of faces, instantly recognising those we know. It’s an innate ability that we rarely think about, and in some ways take for granted. But not everyone has this skill: those with a condition called prosopagnosia – also known as “face blindness” – are simply unable to recognise others by their faces.</p>
<p>Throughout years of research into the condition, I have met many people from all walks of life who suffer from face-blindness. I met <a href="http://www.springer.com/gp/book/9783642407833">Tiffany, for example,</a> in Sydney, Australia. She told me about the earliest experience of prosopagnosia she could remember:</p>
<blockquote>
<p>I was about seven years old. There was a low footbridge which my siblings and I crossed to get from our home to school. It had been washed away during heavy rain, so we were forced to walk about 2km to another bridge. </p>
<p>A man driving past stopped and offered us a lift. My siblings accepted, but I refused as I thought he was a stranger. It turned out he was the priest at the church we all attended each week. I had known him for two years – I did not recognise him because he was in normal clothes.</p>
</blockquote>
<p>As you might expect, living in a world where “all faces look the same” can lead to a multitude of daily struggles, forcing sufferers to avoid certain situations out of fear they won’t be able to recognise familiar people.</p>
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<iframe width="440" height="260" src="https://www.youtube.com/embed/79NVrMQlxvo?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
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<p>Facial recognition is not something that humans learn, rather it is something we are born with. But face-blind sufferers can develop their own coping mechanisms to overcome any problems the condition may cause. They might focus on extra-facial cues such as hairstyle, gait, clothing and jewellery; or on some distinctive facial features such as bushy eyebrows, a big nose, or a face mole instead. What they cannot apparently do is perceive a face as a whole, as a “holistic” stimulus. </p>
<h2>Learning to recognise</h2>
<p>Though prosopagnosia, and <a href="https://theconversation.com/how-an-army-of-super-recognisers-could-help-spot-criminals-and-missing-persons-67571">super recognition at the other end of the spectrum</a>, are now the subject of much research, the disorder is documented as far back as the time of the ancient Greeks. Early descriptions of serious face recognition difficulties come from soldiers <a href="https://books.google.co.uk/books?id=2AfABAAAQBAJ&pg=PA42&lpg=PA42&dq=Peloponnesian+War+facial+recognition&source=bl&ots=VbK3sBmEux&sig=91MEBWszsJLehZ2PBM9rmcqLj9s&hl=en&sa=X&ved=0ahUKEwi8_ePK25jQAhUkCsAKHe3_DDgQ6AEIKTAC#v=onepage&q=Peloponnesian%20War%20facial%20recognition&f=false">injured in the Peloponnesian War</a>. </p>
<p>These historical cases, along with the many others that have been reported much more recently, are cases of acquired prosopagnosia. They describe a form of prosopagnosia that follows a brain injury such as a stroke or head trauma. We now know, however, that prosopagnosia can also exist in people, like Tiffany, who have not been affected by any brain lesion. This second form of prosopagnosia is known as congenital, or developmental, prosopagnosia (CP). CP is not as rare as you might think either: it affects around <a href="https://www.ncbi.nlm.nih.gov/pubmed/19921582">2-2.9% of the general adult population</a> – around 1.5m people in the UK alone.</p>
<p>Our ability to recognise people by their faces is mediated by clusters of neurons that form “face processing areas” in the posterior part of the brain. Our own research has demonstrated that these areas in the brains of those with CP <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/pmc4230164/">work in an atypical way</a>, and do not properly discriminate face from non-face stimuli. </p>
<p>Despite many researchers working to find the causes of CP, we still don’t have a single concrete reason for explaining why these anomalies are present – but we are working on it. Evidence has shown that that, overall, our ability to recognise faces has a <a href="http://www.pnas.org/content/107/11/5238.abstract?ijkey=812fd73874ff75292120f79e1362814a5d53dd44&keytype2=tf_ipsecsha">strong genetic component</a>, and that CP <a href="https://www.ncbi.nlm.nih.gov/pubmed/19334307">runs in families</a>. This suggests that CP may be a genetic condition.</p>
<p>So what can we do to help prosopagnosia sufferers? It is not as simple as sitting someone down to “learn” facial recognition. Though research has found that face-blindness can <a href="http://journal.frontiersin.org/article/10.3389/fnhum.2014.00491/full">be improved with training</a>, there is no simple “cure”. </p>
<p>Our team recently adopted “neuromodulation” to test whether human face recognition can be improved. This is a neuroscientific technique that involves delivering a very small (undetectable) current through the scalp via two small sponge electrodes. We have demonstrated that neuromodulation actually <a href="http://www.sciencedirect.com/science/article/pii/S0028393215302700">leads to improved face-processing skills</a>, and though it is no a “cure”, it does suggest the potential of this approach in future studies aimed at treating CP. </p>
<p>One of our team’s main goals is to find ways to enhance the face processing skills of those suffering with congenital prospagnosia. However, it is currently very difficult to study CP – although there are a large number of sufferers, a relatively small number of people have been <a href="https://theconversation.com/always-forget-a-face-so-does-brad-pitt-dont-just-blame-your-memory-50334">properly diagnosed</a>. This is why we are now <a href="https://www.uel.ac.uk/Schools/Psychology/Research/Prosopagnosia">launching a new website</a>, working with schools and increasing awareness to encourage those who may suffer from the condition to learn more, and to take part in further research.</p><img src="https://counter.theconversation.com/content/67211/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Davide Rivolta 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>We’re working on a ‘cure’ for congenital prosopagnosia.Davide Rivolta, Senior Lecturer in Psychology, University of East LondonLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/578532016-04-15T15:39:29Z2016-04-15T15:39:29ZTelling people apart: new test reveals wide variation in how well we recognise faces<figure><img src="https://images.theconversation.com/files/118928/original/image-20160415-11155-uustgq.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Face blind or super-recogniser?</span> <span class="attribution"><span class="source">Gunter Loffler</span></span></figcaption></figure><p>It’s three o’clock and you are picking up your son from school. The bell rings. A class of six-year-olds charges out of the building. And you have absolutely no idea which child is your son. They all look exactly the same. </p>
<p>This is not a scene from a low-budget horror movie, but how it feels to have <a href="http://www.nhs.uk/conditions/prosopagnosia/Pages/Introduction.aspx">face blindness</a>. It is actually remarkable that most of us are so good at discriminating between faces, since they are all approximately the same – two eyes above a nose above a mouth. Our visual system has had to become highly sensitive to very subtle differences between them. It’s not foolproof, which is why we often see faces in inanimate objects. </p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/118776/original/image-20160414-2614-1ifb50a.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/118776/original/image-20160414-2614-1ifb50a.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/118776/original/image-20160414-2614-1ifb50a.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=600&fit=crop&dpr=1 600w, https://images.theconversation.com/files/118776/original/image-20160414-2614-1ifb50a.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=600&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/118776/original/image-20160414-2614-1ifb50a.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=600&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/118776/original/image-20160414-2614-1ifb50a.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=754&fit=crop&dpr=1 754w, https://images.theconversation.com/files/118776/original/image-20160414-2614-1ifb50a.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=754&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/118776/original/image-20160414-2614-1ifb50a.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=754&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Just another pepper?</span>
<span class="attribution"><a class="source" href="https://www.flickr.com/photos/blakespot/9234512598/in/photolist-f52hSs-3UVrAQ-cCts85-m1NfMs-aK5NU-8QFSiU-8QCLjR-hereTa-4WTKBh-riWetH-4WPp58-8QFN9q-8WtAk3-dpodsB-dNZ8yB-2EKKV9-daoQY3-o7qbF4-akE7zb-fddzUt-oNrap5-ditkH2-3EymNn-8QCL54-pm6tf9-aCReoA-8Pqijw-domNA1-8QCHAX-afrwGG-ayNRvF-8QFRwq-d5ZfMN-aA1YTS-aATYA8-gbDrp6-eZAL2F-92nY8n-bqEZVx-oQt1oT-2GCX7x-aXNNV6-pRmBoU-7c4e4u-pTsbJP-pSY1LP-7fzVDB-pTAjMy-5xufaN-dpHoJL">Blake Patterson</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span>
</figcaption>
</figure>
<p>Face blindness, also known as prosopagnosia, affects <a href="http://onlinelibrary.wiley.com/doi/10.1002/ajmg.a.31343/full">as many as</a> one in 50 people – upwards of one million in the UK alone. Some are born with the condition, while others develop it after a stroke or serious head injury. Either way, sufferers can have otherwise normal vision. </p>
<p>Since faces and their expressions allow us to read someone’s emotions and judge their state of mind, face-blind people are at <a href="http://www.sciencedirect.com/science/article/pii/S0022399908001578">high risk</a> of social embarrassment, isolation, anxiety and depression. They have to develop strategies to cope, such as recognising people by their hair, height, clothes, posture, gait or voice. And still they can be vulnerable – if a friend gets a new hairstyle, for example, they can become unrecognisable. </p>
<p>Though the condition is not curable, it can be very reassuring to be diagnosed and have the nature of the condition explained. Once the person has told those around them, it often makes them less anxious about being labelled arrogant or rude. It means healthcare workers can show patients new strategies to compensate, such as trying to deal with individuals rather than groups of people, and interacting with the same person each time where possible – sticking to the same GP, for instance. </p>
<p><a href="http://brain.oxfordjournals.org/content/early/2014/03/29/brain.awu062.full">Some reports also suggest</a> that intensive training may help improve their facial recognition, though this has not been widely available to date. Then there are legal implications, since someone with face blindness will not be much help at an identity parade. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/118931/original/image-20160415-26305-o2ukqj.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/118931/original/image-20160415-26305-o2ukqj.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/118931/original/image-20160415-26305-o2ukqj.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=424&fit=crop&dpr=1 600w, https://images.theconversation.com/files/118931/original/image-20160415-26305-o2ukqj.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=424&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/118931/original/image-20160415-26305-o2ukqj.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=424&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/118931/original/image-20160415-26305-o2ukqj.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=533&fit=crop&dpr=1 754w, https://images.theconversation.com/files/118931/original/image-20160415-26305-o2ukqj.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=533&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/118931/original/image-20160415-26305-o2ukqj.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=533&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">‘It was …erm’</span>
<span class="attribution"><a class="source" href="http://www.shutterstock.com/pic-259572743/stock-vector-line-up-police.html?src=csl_recent_image-1">Arkela</a></span>
</figcaption>
</figure>
<h2>A testing problem</h2>
<p>It’s actually not easy to test face perception well. Some tests use photographs, but the viewer can get clues from things like clothing or facial expressions. Other tests rely on memorising faces, but again that could be a result of memory rather than face blindness. These tests tend to be much better at dividing the world into people with good and bad face recognition than grading the wide spectrum that likely exists. They also take between ten and 15 minutes, which is not ideal for health professionals. </p>
<p>We <a href="http://www.sciencedirect.com/science/article/pii/S0042698915003624">recently developed</a> a new test that avoids these shortfalls. It uses simplified face images that <a href="http://www.sciencedirect.com/science/article/pii/S0042698902003620">have been synthesised</a> from ordinary photographs. Unlike photographs, however, they can be very precisely modified to make the faces more or less different from one another. It takes only four minutes from start to finish. </p>
<p>Participants are tested on their ability to tell the odd one out among four faces on a computer screen, cycling through 30 different sets over the duration.
The computer monitors show how well the participant is scoring on each set of faces and adapts the difficulty level using an algorithm. Those scoring well get increasingly more similar faces, while strugglers get less similar faces until the test converges on precisely how sensitive someone is. </p>
<p>If you look at the two sets of faces below, for instance, the left set is much easier to differentiate. About 95% of typical adults would be able to spot that the face on the bottom is the odd one out. In the set on the right, only about 25% of typical adults are able to choose the left-hand face correctly. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/118799/original/image-20160414-2617-l0ovbn.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/118799/original/image-20160414-2617-l0ovbn.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/118799/original/image-20160414-2617-l0ovbn.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=304&fit=crop&dpr=1 600w, https://images.theconversation.com/files/118799/original/image-20160414-2617-l0ovbn.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=304&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/118799/original/image-20160414-2617-l0ovbn.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=304&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/118799/original/image-20160414-2617-l0ovbn.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=382&fit=crop&dpr=1 754w, https://images.theconversation.com/files/118799/original/image-20160414-2617-l0ovbn.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=382&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/118799/original/image-20160414-2617-l0ovbn.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=382&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Can you spot the odd one out from each group?</span>
<span class="attribution"><span class="source">Gunter Loffler</span></span>
</figcaption>
</figure>
<h2>What we found</h2>
<p>We tested 52 young adults with no known face-perception difficulties or eyesight or neurological problems. Some turned out to be highly sensitive to small face differences, while others much less so. This confirms that face perception can vary substantially between individuals who are not face-blind. </p>
<p>We then tested a female patient who did have lifelong difficulties with face recognition. When she took some of the established face tests, her score was statistically just outside normal. But the Caledonian face test scored her several times poorer than the norm – even the poorest person in our main group was approximately twice as good at telling faces apart. </p>
<p>In short, our test potentially offers two kinds of benefits. First, it offers a much more sensitive way of detecting face blindness than the current alternatives. Not only could this help healthcare workers decide what level of intervention is necessary, it can be a tool for the intensive training we mentioned earlier: because the test faces are constantly altered by the algorithm, participants can use the test a number of times without becoming familiar with them. </p>
<p>Being able to differentiate between the face-recognition abilities of “normal” people is useful as well. It may help identify people who are particularly good with faces. The police are beginning to use these so-called “<a href="http://www.bbc.co.uk/news/uk-england-34544199">super-recognisers</a>” to review CCTV footage to connect different crimes, while they could also be helpful at border control, for example. Differentiating abilities could also lend more or less weight to different identification witnesses in court cases, of course. </p>
<p>The test is also quick to administer and suitable for use by optometrists, GPs, psychologists and neurologists. It is ready to be used with adults up to the age of 50, while we’re currently doing more work into face recognition in older people. We are optimistic that a major step forward in this field could now be within reach.</p><img src="https://counter.theconversation.com/content/57853/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>The authors do not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and have disclosed no relevant affiliations beyond their academic appointment.</span></em></p>As many as one in 50 people are face blind, meaning they can’t tell one face from another.Gunter Loffler, Professor of Optometry, Glasgow Caledonian UniversityAndrew J Logan, Lecturer in Optometry, University of BradfordGael Gordon, Senior Lecturer, Vision Sciences, Glasgow Caledonian UniversityLicensed as Creative Commons – attribution, no derivatives.