Many people already know that it takes more effort for our brains to conceive a lie than it does for it to articulate the truth. However, a smaller majority is likely aware of the subtle behavioural tells that stem from this discrepancy.

In a new paper published in the Royal Society Open Science journal, a team of researchers from the UK and the Netherlands determined that when we tell a particularly involved lie we tend to mimic the body language of the person we’re lying to.

This is because committing to deception takes up so much cognitive space, we don’t have enough of our facilities left to choreograph natural responses to progressive dialogue. In cognitive psychology, this parroting process is referred to as non-verbal coordination.

“Non-verbal coordination is the tendency to imitate the behaviours of others. Coordination can take place both on a conscious and a more unconscious or automatic level. How much people coordinate with their interaction partner, depends on several factors, including liking and common goals. There is some evidence that the coordination occurrence is also affected by cognitive load. So far, this has only been demonstrated in isolated body part movement,” The Royal Society explained.

If you’ve been binge-watching True Crime files like the rest of the country, you’ve likely seen this in interrogation rooms. Sometimes a subject will parrot questions posed by interrogators before answering. Some will even adopt the same posture. The bigger the lie, the more apparent the interview-interviewee coordination.

In the past, non-verbal coordination was assessed by manually reviewing movements via video data. The new analysis employs motion capture technology in service of a more precise measure of non-verbal coordination and thus the mechanisms that may influence it.

“Studies of the non-verbal correlates of deception tend to examine liars’ behaviours as independent from the behaviour of the interviewer, ignoring joint action. To address this gap, Experiment 1 examined the effect of telling a truth and easy, difficult, and very difficult lies on non-verbal coordination,” the authors explained in the study’s abstract.

“Non-verbal coordination was measured automatically by applying a dynamic time warping algorithm to motion-capture data. In Experiment 2, interviewees also received instructions that influenced the attention they paid to either the non-verbal or verbal behaviour of the interviewer.”

In both experiments, the non-verbal coordination of the participants increased in correspondence to intricate lies. This appeared to occur irrespective of the degree to which interviewees paid attention to their non-verbal behaviour.

Thanks to the innovative devices used by the researchers, they were able to single out cognitive load as a predictive contributor to non-verbal coordination. It was reliable, in fact, you could probably spot someone in the middle of a lie interpersonally with some success.

“Our findings are consistent with the broader proposition that people rely on automated processes such as mimicry when under cognitive load,” the authors concluded.

“Researchers keen to build on our initial evidence and examine this question might usefully use a full-body motion capture system, or even accurate remote systems such as Microsoft Kinect and automated video analysis that will further increase the ecological validity and the applicability of automatic analysis. Such advances in motion capture technologies are allowing researchers to test the role of mimicry in interpersonal cooperation and deception in increasingly unconstrained paradigms.

“The result is that we are beginning to understand how basic interpersonal processes play out in complex, real world scenarios, such as the interview room.”

 

This article was originally published on The Ladders.