Science Says This Is How to Tell if Someone’s Lying

New research out of the University of Edinburgh and published in the Journal of Cognition provides important caution about our instincts when it comes to lying: They’re often wrong. But the research does provide some clues as to where we can look when we think someone might not be telling the truth — to their bodies, rather than their speech patterns.

The study authors found that participants did an excellent job of identifying the speech changes we culturally associate with lying, such as pauses and changes in speech rate. Based on these cues, study participants made judgements that they had witnessed a lie within a few hundred milliseconds. Their reading of the speech patterns was a natural reaction that didn’t require thought, which was exciting to the researchers because “it undermines models in which everything is modular (first we understand the words, then we look at how they were said, then we look at the context, etc.) in favour of a more interactive account (we take lots of aspects of speech into account simultaneously),” lead researcher Martin Corley, Ph.D., a professor at the University of Edinburgh, told Thrive Global. People make social judgements in a complicated and layered, rather than lateral, way.

The problem is, though, that the speech-related lying behaviors study participants identified were actually more prevalent in people who were telling the truth. Perhaps because behaviors like pausing — or interjections like “um” — are culturally associated with lying, the liars in the study instinctively knew to avoid them. Meanwhile the truth-tellers in the study, who weren’t worried about fooling their interlocutors, did not avoid them.

This means that when we look to speech patterns for signs of a lie, we’re likely to get it wrong. But body language, which the study found people often ignore, is another story. “Gestures seem to be more ‘leaky’ than differences in speech,” Corley told Thrive. Whereas speakers seem to be pretty good at suppressing pauses and other verbal cues that listeners associate with deception, they do produce more gestures, perhaps because they are focused on suppressing the verbal cues. If you’re looking to identify a liar, your best bet is to focus not on speech patterns but on body language. In gesture, not in speech, lies the telltale heart of the lie.

So while Corley admits there’s no surefire way to identify a liar, his study does suggest that paying attention to certain body language cues is a great place to start.

Some specific signs of lying to look out for:

Full-body movements

Body movements such as “rocking forwards, backwards or sideways,” and “postural adjustments such as slumping or straightening one’s back,” seemed to correlate with lies in the study.

Clasping hands

Corley noted that clasping hands could also be a sign that someone isn’t being truthful. Busy focusing on their speech, liars often forget to hide the tension in their hands.

Adjusting clothing

Another specific gesture that correlated with lying in the study was adjusting clothing. Like rocking and hand-clasping, adjusting clothing isn’t a surefire sign that someone is lying. But there’s a similar correlation there: As liars suppresses the verbal cues of a lie, their bodies may “leak” some hint of the truth, Corley says.

All that said, one shouldn’t only rely on body language in isolation. Both what someone is saying and how they are acting should be taken into consideration.