tag:theconversation.com,2011:/id/topics/lie-detectors-4520/articlesLie detectors – The Conversation2023-03-06T19:03:27Ztag:theconversation.com,2011:article/2007412023-03-06T19:03:27Z2023-03-06T19:03:27ZLie detection tests have worked the same way for 3,000 years – and they’re still hopelessly inaccurate<figure><img src="https://images.theconversation.com/files/513528/original/file-20230306-22-kq0lr2.jpg?ixlib=rb-1.1.0&rect=50%2C0%2C5615%2C3741&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>Popular culture is fascinated with the ability to detect liars. Lie detector tests are a staple of police dramas, and TV shows such as Poker Face feature “human polygraphs” who detect deception by picking up tell-tale signs in people’s behaviour. </p>
<p>Records of attempts to detect lies, whether by technical means or by skilled observers, go back at least 3,000 years. Forensic science lie detection techniques have become <a href="https://onlinelibrary.wiley.com/doi/10.1111/j.1541-1338.2005.00166.x">increasingly popular</a> since the invention of the polygraph early in the 20th century, with the latest methods involving advanced brain imaging. </p>
<p>Proponents of lie detection technology sometimes <a href="https://www.press.umich.edu/3091709/lying_brain">make grandiose claims</a>, such as a <a href="https://doi.org/10.1007/s11896-022-09566-y">recent paper</a> that said “with the help of forensic science and its new techniques, crimes can be easily solved”.</p>
<p>Despite these claims, an infallible lie detection method has yet to be found. In fact, most lie detection methods don’t detect lies at all – instead, they register the physiological or behaviour signs of stress or fear. </p>
<h2>From dry rice to red-hot irons</h2>
<p>The <a href="https://journals.sagepub.com/doi/10.1177/1529100610390861">earliest recorded lie detection method</a> was used in China, around 1000 BC. It involved suspects placing rice in their mouths then spitting it out: wet rice indicated innocence, while dry rice meant guilty. </p>
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<img alt="" src="https://images.theconversation.com/files/513532/original/file-20230306-1839-hr80u4.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/513532/original/file-20230306-1839-hr80u4.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/513532/original/file-20230306-1839-hr80u4.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/513532/original/file-20230306-1839-hr80u4.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/513532/original/file-20230306-1839-hr80u4.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/513532/original/file-20230306-1839-hr80u4.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/513532/original/file-20230306-1839-hr80u4.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">
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<span class="caption">In ancient China, chewing dry rice was used a way to determine whether a person was speaking the truth or telling lies.</span>
<span class="attribution"><span class="source">Shutterstock</span></span>
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<p>In India, around 900 BC, <a href="http://scholarlycommons.law.northwestern.edu/cgi/viewcontent.cgi?article=2844&context=jclc">one method</a> used to detect poisoners was observations of shaking. In ancient Greece a rapid pulse rate was taken to indicate deceit. </p>
<p>The Middle Ages saw barbaric forms of lie detection used in Europe, such as the red-hot iron method which involved suspected criminals placing their tongue, often multiple times, on a red-hot iron. Here, a burnt tongue indicated guilt. </p>
<h2>What the polygraph measures</h2>
<p>Historical lie detection methods were based in superstition or religion. However, in the early 20th century a purportedly scientific, objective, lie detection machine was invented: the polygraph.</p>
<p>The <a href="https://www.ojp.gov/pdffiles1/nij/grants/228091.pdf">polygraph measures</a> a person’s respiration, heart rate, blood pressure, and skin conductance (sweating) during questioning. </p>
<p>Usually a “control question” about a crime is asked, such as “Did you do it?” The person’s response to the control question is then compared to responses to neutral or less provocative questions. Heightened reactions to direct crime questions are taken to indicate guilt on the test. </p>
<h2>The overconfidence of law enforcers</h2>
<p>Some law enforcement experts claim they don’t even need a polygraph. They can detect lies simply by observing the behaviour of a suspect during questioning.</p>
<p>Worldwide research shows that law enforcers are often <a href="https://doi.org/10.5093/apj2022a4">confident they can detect lying</a>. Many assume a suspect’s nonverbal behaviour reveals deceit. </p>
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<a href="https://images.theconversation.com/files/513539/original/file-20230306-3839-d63rop.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/513539/original/file-20230306-3839-d63rop.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/513539/original/file-20230306-3839-d63rop.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/513539/original/file-20230306-3839-d63rop.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/513539/original/file-20230306-3839-d63rop.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/513539/original/file-20230306-3839-d63rop.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/513539/original/file-20230306-3839-d63rop.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/513539/original/file-20230306-3839-d63rop.jpeg?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">Unlike Poker Face’s ‘human polygraph’, the lie-detection efforts of real-life law enforcers are often fallible.</span>
<span class="attribution"><span class="source">Peacock</span></span>
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<p>A <a href="https://www.emerald.com/insight/content/doi/10.1108/14636641111134314/full/html">2011 study with Queensland police</a> revealed many officers were confident they could detect lying. Most favoured a focus on nonverbal behaviour even over available evidence. </p>
<p>However, <a href="https://link.springer.com/chapter/10.1007/978-3-319-96334-1_3">research shows</a> that law enforcers, despite their confidence, are often not very good at detecting lying. </p>
<p>Law enforcement officers are not alone in thinking they can spot a liar. <a href="https://journals.sagepub.com/doi/10.1177/0022022105282295">Global studies</a> have found that people around the world believe lying is accompanied by specific nonverbal behaviours such as gaze aversion and nervousness.</p>
<h2>What’s really being tested</h2>
<p>Many historical and current lie detection methods seem underpinned by the plausible idea that liars will be nervous and display observable physical reactions. </p>
<p>These might be shaking (such as in the ancient Indian test for poisoners, and the nonverbal behaviour method used by some investigators), a dry mouth (the rice-chewing test and the hot-iron method), increased pulse rate (the ancient Greek method and the modern polygraph), or overall heightened physiological reactions (the polygraph). </p>
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Read more:
<a href="https://theconversation.com/hows-your-poker-face-why-its-so-hard-to-sniff-out-a-liar-25487">How's your poker face? Why it's so hard to sniff out a liar</a>
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<p>However, there are two major problems with using behaviour based on fear or stress to detect lying. </p>
<p>The first problem: how does one distinguish fearful innocents from fearful guilty people? It is likely that an innocent person accused of a crime will be fearful or anxious, while a guilty suspect may not be. </p>
<p>This is borne out with the polygraph’s <a href="https://nap.nationalacademies.org/read/10420/chapter/10#218">high false-positive rate</a>, meaning innocent people are deemed guilty. Similarly, some police have assumed that <a href="https://cqu-primo.hosted.exlibrisgroup.com/permalink/f/1rb43gr/TN_cdi_informaworld_taylorfrancisbooks_9781843926337">innocent, nervous suspects were guilty</a> based on inaccurate interpretations of behavioural observations.</p>
<p>The second major problem with lie detection methods based on nervous behaviour is there is <a href="https://journals.copmadrid.org/apj/art/apj2019a9">no evidence</a> that specific nonverbal behaviours reliably accompany deception.</p>
<h2>Miscarriages of justice</h2>
<p>Despite what we know about the inaccuracy of polygraph tests, they haven’t gone away. </p>
<p>In the US, they are still used in some police interrogations and <a href="https://www.wired.com/story/inside-polygraph-job-screening-black-mirror/">high-security job interviews</a>. In the UK, lie detector tests are used for <a href="https://www.gov.uk/government/publications/domestic-abuse-bill-2020-factsheets/mandatory-polygraph-tests-factsheet">some sex offenders on probation</a>. And in China, the use of polygraphs in law enforcement may <a href="https://www.sciencedirect.com/science/article/abs/pii/S0031938414005964?via%3Dihub">even be increasing</a>.</p>
<p>Australia has been less enthusiastic in adopting lie-detection machines. In New South Wales, the use of lie-detector findings was barred from court in 1983, and an attempt to present polygraph evidence to a court in Western Australia in 2003 <a href="https://www.tandfonline.com/doi/abs/10.1375/pplt.2004.11.2.359">also failed</a>.</p>
<p>Many historical and current lie detection methods emulate each other and are based on the same assumptions. Often the <a href="https://muse.jhu.edu/book/13865">only difference</a> is the which part of the body or physical reacion they focus on.</p>
<p>Using fallible lie detection methods <a href="https://journals.copmadrid.org/apj/art/apj2022a4">contributes to wrongful convictions</a> and miscarriages of justice. </p>
<p>Therefore, it is important that criminal-justice practitioners are educated about fallacious lie detection methods, and any new technique grounded in fear or stress-based reactions should be rejected. </p>
<p>Despite outward appearances of technological advancement, over many millennia little has changed. Fearful innocents remain vulnerable to wrongful assumptions of guilt, which is good news for the fearless guilty.</p><img src="https://counter.theconversation.com/content/200741/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>Most methods for detecting lies actually detect signs of stress – which makes them extremely unreliable.Rebecca Wilcoxson, Lecturer in Forensic Psychology, CQUniversity AustraliaEmma Turley, Senior Lecturer in Criminology, CQUniversity AustraliaLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1304772020-01-24T10:49:22Z2020-01-24T10:49:22ZPolygraph lie detector tests: can they really stop criminals reoffending?<figure><img src="https://images.theconversation.com/files/311803/original/file-20200124-81346-1djzqpg.jpg?ixlib=rb-1.1.0&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/computer-shows-physiological-measures-man-undergoing-1506802802">Gorodenkoff/Shutterstock</a></span></figcaption></figure><p>The UK government <a href="https://www.gov.uk/government/news/tougher-sentencing-and-monitoring-in-government-overhaul-of-terrorism-response">recently announced</a> it was planning to increase the use of polygraphs to monitor offenders on probation, specifically those convicted of terrorist offences.</p>
<p>This is one of several new measures to prevent a repeat of the <a href="https://theconversation.com/london-bridge-attack-why-longer-sentences-for-terrorist-offences-are-not-the-answer-128154">recent London Bridge attack</a>, which was <a href="https://www.bbc.co.uk/news/uk-50611788">committed by</a> an offender out in the community on license. One difficulty with deciding which offenders can be released this way is that offenders can lie about their actions, thoughts and intentions to convince probation officers that they pose a low risk.</p>
<p>The government hopes that an increased use of polygraphs will help identify terrorists planning to reoffend. But are polygraphs actually able to do this?</p>
<p>Polygraphs are already in use in the UK for probation purposes. Since 2014, high-risk sex offenders have had to <a href="https://www.gov.uk/government/news/compulsary-lie-detector-tests-for-serious-sex-offenders">undergo polygraphs testing</a> as part of their license conditions. Sex offenders are also routinely asked to undergo polygraphs <a href="https://www.tandfonline.com/doi/full/10.1080/09540261.2018.1561428">in the US</a>, but the practice is not common in other countries.</p>
<p>Although polygraphs are sometimes known as lie detectors, they <a href="https://www.apa.org/research/action/polygraph">don’t actually detect lies directly</a>. Most modern polygraphs measure the interviewee’s heart rate, breathing rate and sweating while they are asked yes/no questions. These questions need to be simple and refer to a concrete event that is known by the interviewer. This makes it hard to use polygraphs to ask people what they plan to do in the future, because we don’t know enough to know the right questions to ask.</p>
<p>The polygraph picks up on any changes in breathing, heart or sweat rate during the interview. These changes can happen for many reasons. Sometimes a response is caused by the stress of lying. Sometimes they are an “<a href="https://onlinelibrary.wiley.com/doi/full/10.1111/j.1469-8986.00167.x">orienting response</a>”, people responding to something familiar or important to them.</p>
<p>This can be helpful to show that somebody knows something that they said they didn’t know (“<a href="https://psycnet.apa.org/record/2003-04931-014?doi=1">guilty knowledge</a>”). However, strong polygraph responses may also be due to shock or upset at the question or nervousness about the polygraph itself.</p>
<h2>Better than average</h2>
<p>So how accurate are polygraphs in actually detecting lies? There have been <a href="https://www.nap.edu/read/10420/chapter/1">several</a> <a href="https://apoa.memberclicks.net/assets/docs/polygraph_404.pdf">reviews</a> of polygraph accuracy. They suggest that polygraphs are accurate between 80% and 90% of the time. This means polygraphs are far from foolproof, but better than the average person’s ability to spot lies, which <a href="https://psycnet.apa.org/record/2002-11509-006?doi=1">research suggests</a> they can do around 55% of the time.</p>
<p>However, many of these polygraph studies involved people lying about clearly defined events in controlled experiments. It is possible that polygraphs are less accurate in real life probation cases. One <a href="https://www.cambridge.org/core/services/aop-cambridge-core/content/view/288DEA187FE65B40A85FC0DEC5759305/S0007125000231607a.pdf/div-class-title-accuracy-and-utility-of-post-conviction-polygraph-testing-of-sex-offenders-div.pdf">study from 2006</a> attempted to estimate the accuracy of the polygraph with US sex offenders, but it relied on the offenders saying when the polygraph was wrong, which may not be entirely accurate.</p>
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<img alt="" src="https://images.theconversation.com/files/311804/original/file-20200124-81336-z0jeas.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/311804/original/file-20200124-81336-z0jeas.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/311804/original/file-20200124-81336-z0jeas.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/311804/original/file-20200124-81336-z0jeas.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/311804/original/file-20200124-81336-z0jeas.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/311804/original/file-20200124-81336-z0jeas.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/311804/original/file-20200124-81336-z0jeas.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">
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<span class="caption">Who’s telling the truth: the test or the subject?</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-illustration/concept-lies-lie-detector-text-3d-245067355">Maxx Studio</a></span>
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<p>Unfortunately, we don’t know how often probation officers suspect that offenders are lying and how good they are at identifying lies. So, we don’t know whether polygraphs are better than probation officers.</p>
<p>There are also concerns about when the polygraph is wrong. The test can be <a href="https://psycnet.apa.org/record/1985-13834-001?doi=1">beaten by liars</a> with knowledge of how polygraphs work and are used. These people may also be the ones that the probation officers are most interested in catching. They may have practised how to beat polygraphs precisely because they have very serious things to hide.</p>
<p><a href="https://psycnet.apa.org/record/1989-26277-001">Some studies</a> show that polygraphs are worse at detecting that people are telling the truth than detecting they are lying, in some cases indicating deception for almost half of the people who are actually telling the truth. This can be especially difficult to deal with in probation situations, where an offender may have no opportunity to prove that they were not lying when the polygraph indicates they are. How do you prove that you weren’t planning to reoffend? </p>
<h2>Encouraging truth telling</h2>
<p>However, there is another use for polygraphs in probation. They encourage people to confess. Forensic psychologist Theresa Gannon and her colleagues studied this on <a href="https://journals.sagepub.com/doi/pdf/10.1177/1079063213486836">UK sex offenders in 2014</a>. They found that offenders were more likely to disclose something of interest when using the polygraph (75%, instead of 51% without). This disclosure often happened after the polygraph had indicated deception. It may be that offenders feel forced to make a confession after failing the polygraph. However, the study could not tell whether these confessions are true.</p>
<p>After failing a polygraph, offenders may feel that further denials won’t be believed and confessing is best, even when they were not lying. This research suggests that the polygraph can be used to psychologically pressure offenders into disclosing self-incriminating information. Information that may not even be true.</p>
<p>So, is it a good idea for the government to increase polygraph use to monitor offenders? Research shows that they are nowhere near foolproof, but they may have some usefulness as a potential indicator of deception and to encourage truth telling. </p>
<p>However, using them raises several ethical questions. For example, it is fair to use them to try and extract self-incriminating statements?</p>
<p>Some people may argue that something is better than nothing and polygraphs are the best we’ve got. But in instances where polygraphs are so inaccurate that they give probation officers more useless than useful information, nothing may be better than something.</p><img src="https://counter.theconversation.com/content/130477/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Lara Warmelink 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>The UK government is introducing polygraph tests for convicted terrorists on probation.Lara Warmelink, Lecturer, Department of Psychology, Lancaster UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1040432018-09-28T20:17:08Z2018-09-28T20:17:08ZIs a polygraph a reliable lie detector?<figure><img src="https://images.theconversation.com/files/238469/original/file-20180928-48650-wuiayd.jpg?ixlib=rb-1.1.0&rect=155%2C255%2C2709%2C2171&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Does your body give away if you're lying or not?</span> <span class="attribution"><a class="source" href="http://www.apimages.com/metadata/Index/Watchf-AP-A-IL-USA-APHS292554-Crime-Polygraph/a9ad14be6f454cbe9c4799ec9fc21e20/49/0">AP Photo/Edward Kitch</a></span></figcaption></figure><p>Attorneys for Christine Blasey Ford, the woman who’s accused Supreme Court justice nominee Brett Kavanaugh of sexual assault, released the results of a polygraph test focused on the decades-old incident. They suggest that Ford’s responses to two questions about her allegations were “<a href="https://www.cbsnews.com/news/christine-blasey-ford-attorneys-release-polygraph-results-on-kavanaugh-allegations/">not indicative of deception</a>.”</p>
<p>How trustworthy is that assessment and the polygraph technology it relies on?</p>
<p>People have long yearned for some way to separate truth from falsehood, whether in high-stakes court cases or family kerfuffles. Over the years, inventors have developed an evolving assembly of tools and instruments aimed at figuring out whether someone is telling a lie. They’ve tried to incorporate increasingly more science, but with varying degrees of success. Society has often looked to instruments like the polygraph to inject some objectivity into the detection of deception.</p>
<p>As a defense lawyer, I’ve had many a client tell me that he or she did not commit the alleged crime. But I’ve never asked a client to submit to a polygraph exam: It’s high risk, low reward, and the results – while inadmissible in a criminal case – are unpredictable. Just how reliable is a polygraph at identifying who’s lying and who’s telling the truth?</p>
<h2>Looking for signs of lies</h2>
<p>Methods of lie detection have progressed from their <a href="https://scholarlycommons.law.northwestern.edu/cgi/viewcontent.cgi?article=2844&context=jclc">torture-centric</a> roots. Early techniques included subjecting someone to a <a href="https://www.history.com/news/7-bizarre-witch-trial-tests">water test</a>: Those who sank were considered innocent, while floating indicated guilt, lies and witchcraft. Neither outcome was good news for the accused. In medieval Europe, an honest man was thought to be able to <a href="https://doi.org/10.1080/14789940412331337353">submerge his arm in boiling water</a> longer than a liar.</p>
<p>Eventually people developed more humane methods, focusing on physiological factors that could be used as arbiters of truth. In the early 20th century, William Moulton Marston – <a href="https://www.thecrimson.com/article/2017/10/26/william-marston-lie-detector/">self-proclaimed “father of the polygraph”</a> – showed a strong link between systolic blood pressure and lying. Basically, spin a tale and your blood pressure rises. Martson also created the comic book character Wonder Woman, whose golden lasso can extract the truth from those it ensnares.</p>
<p>In 1921, physiologist <a href="https://alumni.berkeley.edu/california-magazine/spring-2010-searchlight-gray-areas/truth-machine">John Larson</a>, from the University of California, Berkeley, was the first to couple measurements of both blood pressure and breathing, looking at rises and drops in respiration. The Berkeley Police Department adopted his device and used it to assess the trustworthiness of witnesses.</p>
<p>In 1939, Larson’s protégé, <a href="https://www.encyclopedia.com/science/encyclopedias-almanacs-transcripts-and-maps/keeler-leonard">Leonarde Keeler</a> updated the system. He made it compact for travel and added a component to gauge <a href="https://imotions.com/blog/gsr/">galvanic skin response</a>, which measures sweat gland activity that could reflect the intensity of an emotional state. His device, purchased by the FBI, was the precursor to the <a href="https://apoa.memberclicks.net/assets/docs/APA-Journal.Articles/Vol.16.1987/polygraph%201987%20161.pdf">modern polygraph</a>. Later versions were variations on this original.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/238472/original/file-20180928-48634-ojkzq2.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/238472/original/file-20180928-48634-ojkzq2.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/238472/original/file-20180928-48634-ojkzq2.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=389&fit=crop&dpr=1 600w, https://images.theconversation.com/files/238472/original/file-20180928-48634-ojkzq2.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=389&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/238472/original/file-20180928-48634-ojkzq2.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=389&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/238472/original/file-20180928-48634-ojkzq2.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=489&fit=crop&dpr=1 754w, https://images.theconversation.com/files/238472/original/file-20180928-48634-ojkzq2.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=489&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/238472/original/file-20180928-48634-ojkzq2.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=489&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Sensors detect changes in how the subject’s body reacts to questions from the examiner.</span>
<span class="attribution"><a class="source" href="http://www.apimages.com/metadata/Index/Science-of-Lying/5aa52099980048f9bb3fd8a694718ab4/2/0">AP Photo/Fernando Vergara</a></span>
</figcaption>
</figure>
<h2>Lie detectors today</h2>
<p>“Lie detector” is a broad term. It most often refers to a polygraph, but also applies to a <a href="https://www.cvsa1.com/cvsa-training.htm">Certified Voice Stress Analysis</a>, an <a href="https://doi.org/10.1037/a0028841">fMRI brain scan</a>, or even software used to <a href="http://www.academia.edu/24786360/Linguistic_Inquiry_Word_Count_LIWC_and_Deception_Detection">analyze the word choice and variation</a> a subject uses when recounting an event. </p>
<p>What today’s polygraph does is encapsulated <a href="https://www.etymonline.com/word/polygraph">in the word itself</a>. “Poly” means many or multiple, and “-graph” means to write. The system records several physiological responses – most often perspiration, heart rate, breathing rate and blood pressure – and graphs them out visually for an examiner to interpret.</p>
<p><iframe id="cWsgo" class="tc-infographic-datawrapper" src="https://datawrapper.dwcdn.net/cWsgo/1/" height="400px" width="100%" style="border: none" frameborder="0"></iframe></p>
<p>There are two most common approaches to administering a polygraph. In what’s called the <a href="http://www.apa.org/research/action/polygraph.aspx">Controlled Question Technique</a>, an examiner will ask irrelevant questions, control questions and relevant questions. Then, based on what he sees in the graphical representation of the subject’s physiological responses, he will identify whether they change significantly in response to relevant questions. The <a href="http://www.apa.org/monitor/julaug04/polygraph.aspx">underlying assumption</a> is that deception will, due to the stress induced by lying, lead to a measurable response in the form of increased perspiration, heart rate and so on.</p>
<p>The second approach is known as the <a href="http://www.apa.org/research/action/polygraph.aspx">Guilty Knowledge Test</a>, which is really a misnomer. It <a href="https://doi.org/10.1108/20093829201100001">tests any knowledge of events</a>, not just guilty knowledge. The examiner measures a subject’s response to specific questions in an attempt to discern whether the subject does in fact have personal knowledge of an event. This could be anything from knowing how many times a victim was stabbed to the color of the getaway car.</p>
<p>Presumably, a person who lacks knowledge of an event would not react significantly differently to the accurate answer because he or she wouldn’t know what’s right and what’s not. Meanwhile, so the logic goes, a person who has firsthand knowledge would demonstrate a physiological response. Of course, this method also <a href="https://www.polygraph.org/assets/docs/APA-Journal.Articles/2009/question_formulation.pdf">has inherent limitations</a> regarding, among other things, what types of questions may be presented.</p>
<h2>Can polygraphs really tell truth from lies?</h2>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/238474/original/file-20180928-48650-3wmz5l.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/238474/original/file-20180928-48650-3wmz5l.png?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/238474/original/file-20180928-48650-3wmz5l.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=600&fit=crop&dpr=1 600w, https://images.theconversation.com/files/238474/original/file-20180928-48650-3wmz5l.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=600&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/238474/original/file-20180928-48650-3wmz5l.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=600&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/238474/original/file-20180928-48650-3wmz5l.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=754&fit=crop&dpr=1 754w, https://images.theconversation.com/files/238474/original/file-20180928-48650-3wmz5l.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=754&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/238474/original/file-20180928-48650-3wmz5l.png?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">An examiner keeps an eye on how various measures change in response to particular topics or questions.</span>
<span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/File:Polygram1.png">DENker/Wikimedia Commons</a></span>
</figcaption>
</figure>
<p>The efficacy of polygraphs is hotly debated in <a href="https://doi.org/10.1126/science.291.5506.967">scientific</a> and <a href="https://www.npr.org/2015/01/02/371925732/trial-of-polygraph-critic-renews-debate-over-tests-accuracy">legal</a> communities. In 2002, <a href="https://www.nap.edu/catalog/10420/the-polygraph-and-lie-detection">a review by the National Research Council</a> found that, in populations “untrained in countermeasures, specific-incident polygraph tests (GKTs) can discriminate lying from truth telling at rates well above chance, though well below perfection.” Better than flipping a coin to figure out whether someone is telling the truth, but far from achieving consistent and reliable results.</p>
<p>The NRC warned against using polygraphs in employment screenings, but it did note that specific-incident polygraph tests in the field yield more accurate results. It seems <a href="https://www.nap.edu/read/10420/chapter/3#23">targeted, relevant questions</a> – for instance, “Was the robbery committed with a gun?” – meant to unmask a subject who may have a strong motive to lie or conceal information seem to work better. </p>
<p>Polygraphs can deliver <a href="http://biostatmatt.com/archives/2919">false positives</a>: asserting that someone is lying who is actually telling the truth. The consequences of “failing” a polygraph can be <a href="https://www.psychologytoday.com/us/blog/the-skeptical-psychologist/200907/the-polygraph-test-strikes-and-strikes-out-again">serious</a> – from not getting a job to being labeled a <a href="https://www.bbc.com/news/magazine-22467640">serial killer</a>.</p>
<p>In the 1998 Supreme Court case <a href="https://en.wikipedia.org/wiki/United_States_v._Scheffer">United States v. Scheffer</a>, the majority stated that “there is simply no consensus that polygraph evidence is reliable” and “[u]nlike other expert witnesses who testify about factual matters outside the jurors’ knowledge, such as the analysis of fingerprints, ballistics, or DNA found at a crime scene, a polygraph expert can supply the jury only with another opinion.” </p>
<p>Notably, litigation over the precursor to the modern polygraph gave rise to the seminal <a href="https://en.wikipedia.org/wiki/Frye_standard">Frye opinion</a> from the D.C. Circuit in 1923, which held that the polygraph evidence was inadmissible in court. In 2005, the 11th Circuit Court of Appeals <a href="https://caselaw.findlaw.com/us-11th-circuit/1259788.html">reiterated</a> that “polygraphy did not enjoy general acceptance from the scientific community.” </p>
<p>The reality is that <a href="https://www.independent.co.uk/life-style/love-island-lie-detector-test-episode-polygraph-fake-dani-jack-danny-dyer-kaz-josh-a8460681.html">multiple factors</a> – including nervousness in a high-stakes situation – can affect the readings detected by a polygraph machine, and give an impression that the subject is lying. For that reason, polygraphs are not generally admissible in any criminal case, even though police interrogators will sometimes <a href="https://www.vox.com/2014/8/14/5999119/polygraphs-lie-detectors-do-they-work">trick a suspect</a> into submitting to one. Polygraphs <a href="https://www.hg.org/legal-articles/is-a-polygraph-test-admissible-as-evidence-31737">may be admissible</a> in civil cases, depending on the state, and some states allow polygraph tests to be used in criminal cases if everyone agrees to it. </p>
<h2>Better than nothing?</h2>
<p>In short, polygraphs may offer some – albeit slight – confidence that a person is telling the truth about a particular incident. Studies have shown that when a well-trained examiner uses a polygraph, he or she <a href="http://dx.doi.org/10.1037/0021-9010.79.2.252">can detect lying with relative accuracy</a>. </p>
<p>But a polygraph is not perfect: An examiner’s interpretation is subjective, and results are idiosyncratic to the person being tested. Under the right circumstances, the polygraph allegedly <a href="https://www.nytimes.com/2015/04/12/magazine/how-to-beat-a-polygraph-test.html">can be fooled</a> by a trained individual. Even some of my forensic evidence students “beat the test” when I bring a polygraph examiner in for a classroom demonstration.</p>
<p>Perhaps the 11th Circuit <a href="https://www.leagle.com/decision/infdco20180205b07">summed it up best</a>: There is no Pinocchio factor associated with polygraphs. As much as we’d like a sign as obvious as a growing nose, there’s no 100 percent reliable physical sign of telling a lie.</p>
<p>A polygraph examination demonstrates “<a href="https://www.leagle.com/decision/infdco20180205b07">that the examinee believes her own story</a>.” And perhaps that’s enough. A subject’s willingness to even submit to an exam often reveals a level of veracity and can fill a void when the other party has not similarly submitted to an exam.</p><img src="https://counter.theconversation.com/content/104043/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Jessica Gabel Cino 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>It would be great to know for sure when someone is lying and when someone is telling the truth. But no technology that purports to do so is foolproof.Jessica Gabel Cino, Associate Dean for Academic Affairs and Professor of Law, Georgia State UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/802632017-08-02T08:39:33Z2017-08-02T08:39:33ZIf a brain can be caught lying, should we admit that evidence to court? Here’s what legal experts think<figure><img src="https://images.theconversation.com/files/180175/original/file-20170728-23788-guf82w.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Functional magnetic resonance imaging could reveal whether someone knows something they're not telling.</span> <span class="attribution"><a class="source" href="http://journal.frontiersin.org/article/10.3389/fneur.2013.00016/full">John Graner et al/Frontiers in Neurology</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span></figcaption></figure><p>A man is charged with stealing a very distinctive blue diamond. The man claims never to have seen the diamond before. An expert is called to testify whether the brain responses exhibited by this man indicate he has seen the diamond before. The question is – should this information be used in court?</p>
<p>Courts are reluctant to admit evidence where there is considerable debate over the interpretation of scientific findings. But a <a href="https://academic.oup.com/jlb/article/3796509/The-limited-effect-of-electroencephalography?searchresult=1">recent study from researchers in the US</a> has noted that the accuracy of such “mind reading” technology is improving. </p>
<p>There are various methods of detecting false statements or concealed knowledge, which vary greatly. For example, traditional “lie detection” relies on measuring physiological reactions such as heart rate, blood pressure, pupil dilation and skin sweat response to direct questions, such as “did you kill your wife?” Alternatively, a <a href="http://theconversation.com/brain-scanners-allow-scientists-to-read-minds-could-they-now-enable-a-big-brother-future-72435">functional magnetic resonance imaging (fMRI)</a> approach uses brain scans to identify a brain signature for lying. </p>
<p>However, the technology considered by the US researchers, known as “brain fingerprinting”, “guilty knowledge tests” or “concealed information tests”, differs from standard lie detection because it claims to reveal the fingerprint of knowledge stored in the brain. For example, in the case of the hypothetical blue diamond, knowledge of what type of diamond was stolen, where it was stolen, and what type of tools were used to effect the theft.</p>
<p>This technique gathers electrical signals within the brain through the scalp by electroencephalography (EEG), signals which indicate brain responses. Known as the <a href="https://www.rroij.com/open-access/the-p300-wave-of-eventrelatedpotential.php?aid=34978">P300 signal</a>, those responses to questions or visual stimuli are assessed for signs that the individual recognises certain pieces of information. The process includes some questions that are neutral in content and used as controls, while others probe for knowledge of facts related to the offence. </p>
<p>The P300 response typically occurs some 300 to 800 milliseconds after the stimulus, and it is said that those tested will react to the stimulus before they are able to conceal their response. If the probes sufficiently narrow the focus to knowledge that only the perpetrator of the crime could possess, then the test is said to be “accurate” in revealing this concealed knowledge. Proponents of the use of this technology argue that this gives much stronger evidence than is possible to get through human assessment.</p>
<p>Assuming this technology might be capable of showing that someone has hidden knowledge of events relevant to a crime, should we be concerned about its use?</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/176612/original/file-20170703-4580-1c1nqcr.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/176612/original/file-20170703-4580-1c1nqcr.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=499&fit=crop&dpr=1 600w, https://images.theconversation.com/files/176612/original/file-20170703-4580-1c1nqcr.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=499&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/176612/original/file-20170703-4580-1c1nqcr.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=499&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/176612/original/file-20170703-4580-1c1nqcr.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=627&fit=crop&dpr=1 754w, https://images.theconversation.com/files/176612/original/file-20170703-4580-1c1nqcr.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=627&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/176612/original/file-20170703-4580-1c1nqcr.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=627&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">How private are our memories?</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/cute-girl-colorful-glowing-photo-memories-246693712?src=wiIuEZYLCMwWJVX1yAjxjQ-1-18">ESB Professional/Shutterstock</a></span>
</figcaption>
</figure>
<h2>Potential for prejudice</h2>
<p>Evidence of this sort has not yet been accepted by the English courts, and possibly never will be. But similar evidence has been admitted in other jurisdictions, including India. </p>
<p>In the Indian case of <a href="http://www.nytimes.com/2008/09/15/world/asia/15brainscan.html">Aditi Sharma</a> the court heard evidence that her brain responses implicated her in her former fiancé’s murder. After investigators read statements related and unrelated to the offence, they claimed her responses indicated experiential knowledge of planning to poison him with arsenic, and of buying arsenic with which to carry out the murder. The case generated much discussion, and while she was initially convicted, this was later overturned. </p>
<p>However, the Indian Supreme Court has <a href="http://www.thehindu.com/migration_catalog/article16297234.ece/BINARY/Supreme%20Court%20judgement%20on%20narco-analysis%20test%20(833%20Kb)">not ruled out the possibility of such evidence being used</a> if the person being tested freely consents. We should not forget that people may knowingly conceal knowledge of facts relevant to a crime for all sorts of reasons, such as protecting other people or hiding illicit relationships. These reasons for hiding knowledge may have nothing to do with the crime. You could have knowledge relevant to a crime but be totally innocent of that crime. The test is for knowledge, not for guilt.</p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/176644/original/file-20170703-17450-u7v7lb.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/176644/original/file-20170703-17450-u7v7lb.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/176644/original/file-20170703-17450-u7v7lb.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=705&fit=crop&dpr=1 600w, https://images.theconversation.com/files/176644/original/file-20170703-17450-u7v7lb.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=705&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/176644/original/file-20170703-17450-u7v7lb.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=705&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/176644/original/file-20170703-17450-u7v7lb.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=886&fit=crop&dpr=1 754w, https://images.theconversation.com/files/176644/original/file-20170703-17450-u7v7lb.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=886&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/176644/original/file-20170703-17450-u7v7lb.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=886&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">How much weight is placed on neuroscientific evidence in the courtroom?</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-vector/balance-weight-head-silhouette-graphic-design-330801134">Studio_G/Shutterstock</a></span>
</figcaption>
</figure>
<h2>Context is key</h2>
<p>The US researchers looked at whether brain-based evidence might unduly influence juries and prejudice the fair outcome of trials. They found concerns that <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2778755/">neuroscientific evidence may adversely influence trials</a> could be overstated. In their experiment, mock jurors were influenced by the existence of brain based evidence, whether it indicated guilty knowledge or the absence of it. But the strength of other evidence such as motive or opportunity weighed more heavily in the hypothetical jurors’ minds.</p>
<p>This is not surprising, as our <a href="https://academic.oup.com/jlb/article/2/3/510/1917949/The-use-of-neuroscientific-evidence-in-the?searchresult=1">case-based research</a> demonstrates the importance of the context in which neuroscientific evidence is introduced in court. It could help support a case, but the success is dependent on the strength of all the evidence combined. In no case was the use of neuroscientific evidence alone determinative of the outcome, though in several it was highly significant.</p>
<p>Memory detection technologies are improving, but even if they are “accurate” (however we choose to define that term) it does not automatically mean they will or should be allowed in court. Society, legislators and the courts are going to have to decide whether our memories should be allowed to remain private or whether the needs of justice trump privacy considerations. Our innermost thoughts have always been viewed as private; are we ready to surrender them to law enforcement agencies?</p><img src="https://counter.theconversation.com/content/80263/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>Using mind reading technologies in court could become common practice.Lisa Claydon, Senior Lecturer in Law, The Open UniversityPaul Catley, Head of Law School, The Open UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/281672014-07-17T16:14:29Z2014-07-17T16:14:29ZLie detectors and the lying liars who use them<figure><img src="https://images.theconversation.com/files/52366/original/y3d4bz53-1403796063.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">No, I did not get a manicure before coming here today.</span> <span class="attribution"><span class="source">Polygraph Shutterstock</span></span></figcaption></figure><p>As society becomes more and more dependent on machines to make important decisions, the use of technology for lie detection is becoming increasingly popular. But as much as we would like to rely on technology to give us definitive answers, humans may well always be able to beat the lie detector.</p>
<p>Authorities have traditionally been cautious about using lie detectors but they appear to be warming to the idea. Lie detectors are most readily associated with the police but other authorities have started to get in on the act. Around <a href="http://www.theguardian.com/society/2014/mar/10/councils-use-lie-detector-tests-benefits-fraudsters">20 councils in England</a> are already using or plan to use lie detector tests to try to identify fraudulent benefits claimants, and UK prisons recently announced that around 1,000 of the UK’s most high-risk sex offenders are to undergo <a href="https://www.gov.uk/government/news/compulsary-lie-detector-tests-for-serious-sex-offenders">mandatory lie detector tests</a>.</p>
<p>This is all somewhat surprising given that some of the technologies that form the very foundation of these devices <a href="https://theconversation.com/sounding-like-a-liar-doesnt-make-you-a-benefits-cheat-24310">simply aren’t reliable</a>.</p>
<h2>Lying to ourselves</h2>
<p>There are currently several options to choose from when it comes to lie detection technology. The best known method is the traditional polygraph test, which involves monitoring your pulse, breathing, blood pressure and skin conductivity to measure your physiological responses to questions. Other non-invasive technologies include analysing facial expressions with computer vision techniques and measuring facial temperature profiles with thermal imaging systems.</p>
<p>There have been technological advances in recent years but none are foolproof. Most modern systems based on automated facial analysis rely on computer vision technologies to identify and track a face in real time and machine intelligence techniques to make decisions.</p>
<p>The system will first look at the expressions a person uses under normal, unstressed conditions and uses those as a baseline when they take the lie detector test. Cues such as asymmetries in facial expressions, shifting gaze and a changed rate of blinking are often associated with strong emotion so if the machine detects unusual variations from the baseline then it is often assumed that the subject is lying.</p>
<p>Reliability can be increased by incorporating various other features, such as voice and facial temperature profile. However, at best, these systems can still only identify when subjects are lying or telling the truth roughly 80% of the time. Our own <a href="http://www.sciencedomain.org/abstract.php?iid=423&id=5&aid=3553#.U6w5x9jji71">experiments</a> under lab conditions confirm this. </p>
<p>Lie detection is incredibly difficult even for humans. In general, we can detect a lie only about 54% of the time. But that in itself tells us something interesting, if a little dispiriting. We may not be very good detectors of lies, but as a species we are incredibly good at lying.</p>
<p>Our ability to deceive may even be what has enabled us to dominate the planet. Humans and animals lie for their own gain – be it to avoid danger or gain some sort of advantage over competitors – and can be associated with survival.</p>
<p>The more intelligent an animal is, the more likely it is to lie, which puts us humans right at the top of the ladder. <a href="http://journal.frontiersin.org/Journal/10.3389/fnhum.2012.00087/full">Research</a> has also shown that the best liars are also the best at detecting lies. So are humans becoming better and better at deceit? As a species we’re certainly becoming more intelligent. A phenomenon known as the <a href="http://www.ted.com/talks/james_flynn_why_our_iq_levels_are_higher_than_our_grandparents">Flynn effect</a> bears this out. IQ test comparisons indicate that between the 1900s and today, Americans have gained three IQ points per decade. That’s something that anyone hoping to make a working lie detector should consider.</p>
<p>Given our increasing intelligence and the fairly basic methods used in lie detection, it seems unlikely that we’ll produce lie detectors that can pass muster in the near future. We have yet to fully understand the underlying psychological processes of lying so asking a machine to code it is ambitious, to say the least.</p>
<p>Many will argue that until lie detectors can be made 100% foolproof, they should not be accepted in courts or used in decision making processes. However, the important point to note here is that modern lie detectors, especially those that are non-invasive, can serve as very useful tools which will assist and work alongside with experienced human interrogators. Whatever their future, lie detectors have already made their mark and are here to stay. </p><img src="https://counter.theconversation.com/content/28167/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Hassan Ugail have received funding from EPSRC and DSTL (MoD).</span></em></p>As society becomes more and more dependent on machines to make important decisions, the use of technology for lie detection is becoming increasingly popular. But as much as we would like to rely on technology…Hassan Ugail, Professor of Visual Computing, University of BradfordLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/243102014-03-13T06:19:56Z2014-03-13T06:19:56ZSounding like a liar doesn’t make you a benefits cheat<figure><img src="https://images.theconversation.com/files/43742/original/878y7vtc-1394647050.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">You can't tell if someone's lying by listening to their voice and councils should know that by now.</span> <span class="attribution"><a class="source" href="http://www.flickr.com/photos/cizake/4164756091/sizes/o/">Florian Seroussi</a>, <a class="license" href="http://creativecommons.org/licenses/by-nc-sa/4.0/">CC BY-NC-SA</a></span></figcaption></figure><p>Councils are facing questions about their use of <a href="http://www.theguardian.com/society/2014/mar/10/councils-use-lie-detector-tests-benefits-fraudsters">lie detectors</a> in attempts to catch benefits cheats over the phone. The idea is to listen out for subtle changes in the voice that might indicate that someone isn’t telling the truth about their circumstances.</p>
<p>But there are serious concerns about the technology being used and a chronic lack of evidence to support the claims made about it.</p>
<p>The UK government first tried out <a href="http://www.independent.co.uk/news/uk/crime/lie-detectors-to-assess-if-paedophiles-will-reoffend-6168950.html">lie detection tools</a> with offenders in 2004, despite findings from the US <a href="http://books.google.co.uk/books?id=4WR0AAAAQBAJ&pg=PA102&lpg=PA102&dq=%E2%80%98progressed+over+time+in+the+manner+of+a+typical+scientific+field%E2%80%99+lie+detection+national+research+council&source=bl&ots=cBcePpaf5z&sig=z3ty1F6Vk2KPzwpiRfkiB5tMllQ&hl=en&sa=X&ei=NHcgU9HAO6nT7AaLvIHAAg&ved=0CC0Q6AEwAA#v=onepage&q=%E2%80%98progressed%20over%20time%20in%20the%20manner%20of%20a%20typical%20scientific%20field%E2%80%99%20lie%20detection%20national%20research%20council&f=false">National Research Council</a> that suggested research in this area had not “progressed over time in the manner of a typical scientific field”. In a 2003 assessment, the council warned that research into testing for deception using physiological monitors had failed to “strengthen its scientific underpinnings in any significant manner”.</p>
<p>The main problem is that both voice stress analysis software and the polygraph, which monitors blood pressure, are based on the assumption that liars are more behaviourally aroused than truth tellers because they are afraid of being caught. In reality, displays of arousal depend on many factors, not least the circumstances in which we tell a lie, the individual differences between people and how serious the lie is or the potential repercussions of being found out.</p>
<p>In fact, liars often fail to show an increase in arousal. This can be attributed to a number of causes. Liars do not necessarily experience a fear of being caught or may even be able to control their level of arousal during a test.</p>
<p>On the other hand, truth tellers may show increased arousal due to a fear of not being believed. In the case of the UK government’s attempts to bring in lie detection, this might mean a fear of losing benefits.</p>
<h2>Lying or just stressed?</h2>
<p>The voice stress analyser, or voice risk analyser, uses microphones attached to computers to detect and display readings for the intensity, frequency, pitch, harmonics and micro-tremors of the voice.</p>
<p>This is based on established theory, conducted via empirical research, that changes to the voice indicate stress or arousal. When we are aroused our muscles tense and tighten and, when this happens, these muscles vibrate at a higher frequency leading to an increase in pitch.</p>
<p>When voice stress analysis was first developed, it was hailed as an alternative to the polygraph because it is a non-invasive process and can even be conducted without the person being tested even knowing. Unfortunately, this is the only improvement on the polygraph. The only real difference between the two is that a different physiological response is being measured.</p>
<p>Both techniques suffer from methodological and theoretical problems, particularly if those conducting the test don’t spend time asking the examinee to lie and tell the truth in response to a series of control questions to test their responses first. Without this, there is no comparison between how an individual behaves when being truthful compared to when they lie.</p>
<p>They key point is that voice stress analysis offers a measure of stress or arousal and this is not the same as measuring deception. There is still an insignificant amount of data to link the signs of stress and negative emotion in the human voice with lying.</p>
<p>Despite disappointing results from numerous <a href="http://www.sciencedirect.com/science/article/pii/S0167876005001364">scientific studies</a>on the validity of these systems, voice analysis continues to be popular and several manufacturers produce variations of voice analysis software, which are sold as user-friendly computer devices. There is no evidence to suggest that these programs work at a level any better than chance.</p>
<p>Even ignoring the lack of any empirical support for its application, voice stress analysis is an outdated tool. Recent advances in the area of deception detection acknowledge that you need to take a multi-channel approach, looking at both verbal and non-verbal behavioural cues while taking context into account.</p>
<p>This is one of the aims of on-going research being conducted within the <a href="http://www.uclan.ac.uk/research/environment/groups/emotions_credibility_and_deception_group.php">Centre for Emotions, Credibility and Deception</a> at the University of Central Lancashire. While technology, and in particular measures of real-time body motion and language use, undoubtedly have much to contribute to the field of deception detection, we need to ensure that the work is carried out in a rigorous manner, and is based on sound methodology and theory. Voice stress analysis is not.</p><img src="https://counter.theconversation.com/content/24310/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Beth Helen Richardson 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>Councils are facing questions about their use of lie detectors in attempts to catch benefits cheats over the phone. The idea is to listen out for subtle changes in the voice that might indicate that someone…Beth Helen Richardson, Senior Research Fellow, University of Central LancashireLicensed as Creative Commons – attribution, no derivatives.