Lying makes us mimic the body language of the people we are talking to

When telling a lie, people may imitate the body language of the person they are lying to without realising they are doing it. The discovery might eventually lead to a new form of lie detection test.

“Liars often deliberately change their behaviour into a way they think truth-tellers behave, but this particular copycat behaviour is something they wouldn’t even try to manipulate because they don’t realise they’re doing it,” says Sophie van der Zee at Erasmus University Rotterdam in the Netherlands. “And that could make it an interesting cue for detecting deceit.”

Van der Zee and her colleagues asked about 50 university students to solve a supposedly simple wooden puzzle within 5 minutes. In reality, the puzzle was far too hard to solve in the time available.

Van der Zee “hid” the puzzle solutions in the room where the students could find them, which encouraged the students to cheat. She then asked the students not to tell her supervisor that she had “accidentally” left the solutions in the room because she feared professional consequences. …

This may be because lying requires so much concentration, says van der Zee, so speakers might subconsciously slip into mimicking their listener’s subtlest body movements because copying requires less thinking than coming up with their own body language. This way of coping with “cognitive overload” isn’t obvious to the naked eye, but was detectable with the accelerometers.

It is a “fascinating” study that provides good “basic research” for possible future courtroom use if validated in more in-depth studies, says Tim Brennen at the University of Oslo in Norway.

By Christa Lesté-Lasserre, The New Scientist

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