A good liar is like a chameleon.
In a new study, researchers have identified a strong sign of fibbing: mimicking the body language of the person they’re lying to.
“A liar and a copycat,” the title of the new study now published in the Royal Society’s Open Science journal, could later lead to applications of the theory in criminal justice, New Scientist reported on Friday.
“Liars often deliberately change their behavior into a way they think truth-tellers behave, but this particular copycat behavior is something they wouldn’t even try to manipulate because they don’t realize they’re doing it,” said Sophie Van Der Zee, researcher at Erasmus University Rotterdam in the Netherlands.
“That could make it an interesting cue for detecting deceit,” she told New Scientist.
The study asked university students to solve a puzzle while under the impression that the task should take five minutes or fewer. In reality, the riddle was much harder than the time they were allotted.
Van Der Zee encouraged cheating by providing clues to solve the puzzle, then pretended to confess that she’d left them there “accidentally” — asking the students not to inform her supervisor of the slip-up, but to feel free to use the hints.
Participants, strapped into highly sensitive motion trackers, weren’t aware that it wasn’t their puzzle-solving ability that researchers hoped to monitor, but how they discussed the task. If they heeded Van Der Zee’s request, they’d be forced to lie about how they successfully solved the difficult puzzle by using the clues.
On observation, researchers found that the liars tended to mirror the body language of the person with whom they spoke about the puzzle, whereas honest participants moved differently from their conversational counterpart.
Van Der Zee believes the mental load of lying might be too much for our brains, which resort to copycat behavior while the intellectual mind is focused on crafting their deception. Unfortunately, these subtle changes can be difficult to notice without laboratory tools.
Researchers conclude the study is limited in its findings, as the motion sensors couldn’t determine who was imitating whom, which means the reverse is also possible — that the innocent may be mimicking the liar.