How to spot a liar and it's not what you think
Published 11/12/2015 | 15:19
If you think you can spot a liar by their shifty gaze and hesitant manner you might need to think again.
New research suggests that the most untruthful people are likely to look you straight in the eye and give confident, well though-out responses.
They are also likely to grimace, make excessive hand gestures and use more vocal fill words such as ‘um’ and ‘err,’ according to experts at the University of Michigan.
The researchers have developed the first life-detecting software based on video footage of 120 court cases in the US which can spot someone who is lying 75 per cent of the time. In comparison, humans could spot a liar just 50 per cent of the time, no better than flipping a coin.
Previously psychologists and law enforcers have believed that liars tend to give hesitant answers and will often avoid eye contact. But the new study suggests the opposite and is likely to be more accurate because previous studies have been based on lab experiments.
"In laboratory experiments, it's difficult to create a setting that motivates people to truly lie. The stakes are not high enough," said Dr Rada Mihalcea, professor of computer science and engineering who leads the project
"We can offer a reward if people can lie well--pay them to convince another person that something false is true. But in the real world there is true motivation to deceive."
The team used video footage from both defendants and witnesses in high-stakes hearings, such as murder trials, transcribing their words and counting gestures.
In the clips, the subject was deemed to be lying or telling the truth based on how their testimony aligned with the trial verdicts. The team then fed the data into a computer which produced an algorithm which looked for the most common patterns of liars.
The software could identify a liar 75 per cent of the time, based on several ‘tells’ – slips in behaviour or speech which give away that the subject is lying.
People who lied were three times more likely to scowl or grimace, rather than keeping an open, relaxed face. Liars were also more likely to look directly at the questioner, gesture with both hands and use language to distance themselves from the proceedings – by using ‘he’ or ‘she’ rather than ‘I’ and ‘we.’
"People are poor lie detectors," added Dr Mihalcea. "This isn't the kind of task we're naturally good at.
“There are clues that humans give naturally when they are being deceptive, but we're not paying close enough attention to pick them up. We're not counting how many times a person says 'I' or looks up. We're focusing on a higher level of communication."
The team are hoping to make the test more accurate by adding in physiological signs such as heart rate, respiration rate and fluctuations in body temperature, which can be picked up remotely. People are known to sweat more when the lie, and their breathing rate and heartbeat also goes up.
It means that in the future, a witness or defendant could be given a lie detector test without needing to be wired up to a machine.
"We are integrating physiological parameters such as heart rate, respiration rate and body temperature fluctuations, all gathered with non-invasive thermal imaging," Burzo said.
The researchers are also exploring the role of cultural influence.
"Deception detection is a very difficult problem," added Mihai Burzo, assistant professor of mechanical engineering at the University of Michigan. "We are getting at it from several different angles."
The research was presented at the International Conference on Multimodal Interaction and is published in the 2015 conference proceedings.