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.