How to Spot a Liar

Humans are pretty unreliable lie detectors, so researchers have developed software to sort fact from fiction for us.

People aren't reliable lie detectors. Our unconscious minds can detect when someone is untrustworthy, but our conscious awareness gets in the way and hinders judgement, past studies have found.

Machines aren't so easily confused.

University of Michigan researchers have developed a program that can detect when someone is lying with 75 percent accuracy. Compare that to polygraph tests, whose ability to detect a lie correctly varies depending on whom you ask.

Truth or Lie: How to Tell: Photos

The American Polygraph Association claims their examiners are capable of exceeding a 90 percent accuracy rate, but critics claim a rate closer to 70 percent. The use of polygraphs is also controversial. Although the results of tests are inadmissible in a courtroom, lie detector tests are frequently used in hiring situations or background checks.

Unlike a polygraph test that uses physiological cues to determine whether a subject is being truthful, the software parses words and gestures to analyze honesty. And rather than relying on an experimental setting to train the program, the researchers instead used video footage from real court cases, the outcomes of which determined whether a witness or defendant had been deceptive.

The software correctly determined deception in roughly three-quarters of the cases it analyzed, while human lie detectors who had just slightly better than a 50-50 chance of being able to deduce who was lying.

Practice Makes the Perfect Liar

Using their software, the Michigan team determined a set of behavior patterns more common in liars than in those telling the truth. Liars were more likely to scowl, gesture with both hands and - somewhat unexpectedly - gaze at the questioner. Individuals not telling the truth were also more likely to use nonverbal bridges like "um" or "uh."

Truth-tellers, on the other hand, have more of a tendency to raise their eyebrows, close their eyes and shake their heads. The honest witnesses and defendants were also more likely to use first-person pronouns in their testimony.

Pairing the software's analysis of subtle behavioral and verbal cues with physiological data measured using a polygraph or non-invasive thermal imaging, as the Michigan researchers have begun exploring, could improve the accuracy rate of results.

Video: Why Liars Are More Creative

Brain scans using functional magnetic resonance imaging (fMRI) could also take lie detection one step further, according to an article published last year in the International Journal of Liability and Scientific Enquiry. Brain regions known to be more active when we lie would light up during a scan.

Could lie detectors ever get to the point where they're 100 percent accurate? Any researcher will tell you the answer to that is no, of course. Scientists and engineers can develop new ways of detecting lies, but there will always be individuals using their ingenuity to beat the test. Committed liars are more creative after all; it's what they do.

April 25, 2012 -

Did John Edwards work with his aide to hide his affair or didn't he? Edwards, the former North Carolina senator, faces up to 30 years in prison and $1.5 million in fines if he is found guilty on six charges of violating campaign finance laws, allegedly paid off to his mistress Rielle Hunter. As his trial plods along, there are certain tells, experts say, that reveal when a person is lying -- whether that be him or his aide, Andrew Young. But as detective shows and police know, liars always have their tells. In this slideshow, we take a look at the ways liars show their true colors.

Even if a liar can put on his or her best poker face, unconscious emotional "cracks" -- or unintentional and brief flashes of emotion -- give away a subject's real mental state, according to a study by Stephen Porter's Forensic Psychology Lab at Dalhousie University.

Although sudden cracks in facial expression could give away subtle clues to deception, one researcher found that tiny movements in facial muscles -- such as the zygo maticus major and the orbicularis oculi -- can unmask liars. Social psychologist Mark Frank used computer technology to analyze facial expressions, following a large body of research "about the evolutionarily-derived nature of emotion and its expression," according to a press release on EurekAlert!. Micro-expressions in subjects' faces, such as tics, smiles, frowns and wrinkles, essentially serve as accurate windows into the emotions, even if the person being interrogated is trying to suppress his or her feelings. Frank's system can be used not only to uncover potential criminals, but also even reveal terrorist threats. Frank, however, is quick to point out that his system only provides investigators with "very good clues" and "not proof of anything."

The Eagles may have been on to something. Eyes may reveal a liar in the act, and scientists at the University of Utah have developed technology to detect just that, as reported by Discovery News' Tracy Staedter in 2010. A computer camera and tracking software record minute eye movements to measure cognitive reaction. By contrast, a polygraph measures a subject's emotional reaction. The system "also records other variables, including the time it takes to respond to a question, how long it takes a subject to read or even reread a question and how many errors are made," according to the report. The researchers hope that the technology will be adopted by various U.S. defense, intelligence and law enforcement agencies that regularly employ polygraph tests.

As anyone who has ever dealt with a bad liar before can attest, some people just can't keep a story straight. But even the most talented studied storyteller can fall into some familiar speech patterns that indicate a truthful tale. In a study published in American Journal of Forensic Psychiatry, UCLA professor of psychology R. Edward Geiselman and his colleagues reveal speech patterns they have detected that are often red flags for deceit. Liars very often provide few details, have a tendency to repeat questions, actively monitor listener reactions, speak in sentence fragments and more. To unmask dishonesty, Geiselman and colleagues suggest listeners have potential deceivers tell their story backwards, ask open-ended questions and never interrupt.

If the source of every lie is the brain, shouldn't it be possibly to simply see if that particular region of the brain associated with deceit is active when a subject is lying? Scientists are attempting to use functional-magnetic-resonance-imaging (fMRI) as a lie detector. In a study published in the Proceedings of the National Academy of Sciences in 2009, Joshua Greene, an assistant professor of psychology at Harvard University, found that "areas within the volunteers' prefrontal cortices registered vigorous activity," according to a report on However, as Greene admits, the technique can't tell the difference between someone who intends to lie and a person who is contemplating whether to lie. Despite the limitations of this kind of technology, at least two companies have offered lie detection services using the same technique. This application  has led some scholars to criticize these lie detection methods as no better than the polygraph. Even though these kinds of studies currently have their detractors, the efforts aren't without warrant. A 2005 study out of the University of Southern California and published in the British Journal of Psychiatry found brain abnormalities in people who are habitual liars. "The liars had significantly more 'white matter' and slightly less 'gray matter' than those they were measured against," according to a press release available on Science Daily. The wiring in the brain, white matter may help liars with the extra cognitive effort needed to fabricate information.

Liars may not actually have their pants on fire, but their faces sure seem to heat up when they're not telling the truth, according to a study led by the Mayo Clinic and published in Nature in 2002. In 80 percent of cases studied for the experiment, heat patterns in the face change dramatically when a person is lying. Using high-definition thermal imaging technology, an investigator can monitor these heat patterns to assess the veracity of a subject's statements.

Although handwriting analysis is often regarded as a pseudoscience, it may have a potentially legitimate application in assisting with lie detection, according to researchers at the University of Haifa in Israel. Using a computerized tool to detect a user's hand movements, the researchers found that certain cues, such as "the duration of time that the pen is on paper versus in the air; the length height and width of each writing stroke;

the pressure implemented on the writing surface," can signal when someone is about to write an untruthful statement, according to a release in Science Daily. This technology is intended to work in tandem with verbal-based lie detectors.