How to tell if someone is lying to you: Watch to see if they mimic your actions
- Researchers used motion capture technology to monitor volunteer movements
- They had people tell the truth and increasingly complicated lies to interviewers
- As the lies became more complex the liars began to mimic interviewer motions
- This suggests that we mimic non-verbal language as brain activity increases
Liars begin to mimic the actions of their interviewers questioning them about the whoppers they’ve been spinning, a new study has revealed.
Dutch researchers from Erasmus Universiteit Rotterdam used motion capture to monitor the behaviour of liars as they told increasingly bigger lies to someone else.
We can imitate the behaviour of others unconsciously, and we become more likely to automatically mimic them if the brain is working hard, the researchers explained.
Because it’s harder for the brain to be dishonest than to tell the truth, we tend to mimic our victims when we’re being deceitful, they added.
Dutch researchers from Erasmus Universiteit Rotterdam used motion capture to monitor the behaviour of liars as they told increasingly bigger lies to someone else
As part of the study, which included researchers from the UK and the Netherlands, volunteers were monitored as they told the truth and as they told progressive lies.
The first experiment examined the effect of telling a truth and easy, difficult and very difficult lies on nonverbal coordination – body language and movements.
Nonverbal coordination was measured automatically through motion-capture data.
In the second experiment interviewees also received instructions that influenced the attention they paid to either the nonverbal or verbal behaviour of the interviewer.
Results from both experiments found that interviewer–interviewee nonverbal coordination – mimicking body language – increased with lie difficulty.
This increase was not influenced by the degree to which interviewees paid attention to their nonverbal behaviour, nor by the degree of interviewer’s suspicion of lying.
‘Our findings are consistent with the broader proposition that people rely on automated processes such as mimicry when under cognitive load,’ the team wrote.
Nonverbal coordination is the tendency to imitate the behaviours of others, the team behind the study explained, adding this imitation takes place both on a conscious and a more unconscious – or automatic – level.
The amount someone coordinates nonverbal communications with someone they are interacting with depends on a number of factors – including common goals.
‘There is some evidence that the coordination occurrence is also affected by cognitive load,’ the team explained.
‘A forensically relevant setting that is strongly associated with increased cognitive load is deception. Lying, especially when fabricating accounts, can be more cognitively demanding than truth telling,’ they wrote.
They were able to demonstrate that ‘interactional nonverbal coordination’ increases as the amount of brain powered required for the communication increases.
Because it’s harder for the brain to be dishonest than to tell the truth, we tend to mimic our victims when we’re being deceitful, they added
This was particularly the case when someone was lying to a partner – particularly when they were telling a big lie. Under those circumstances the liar was more likely to mimic the movements and actions of their partner the bigger the whopper got.
‘Nonverbal coordination is an especially interesting cue to deceit because its occurrence relies on automatic processes and is therefore more difficult to deliberately control,’ according to the researchers.
‘Our findings complement current deception research into the liar’s nonverbal behavior by explicitly considering the interaction with the interviewer.
‘Our findings extent the current literature on increased reliance on automated processes by demonstrating that nonverbal coordination can be such an automated process that is affected by increased cognitive load.’
That is, the more your brain has to work to spin a web of untruths, the more your body automatically mimics the actions of the person you are lying to.
‘The use of motion capture technology provides a novel, objective and efficient means of measurement,’ the team explained.
The findings have been published in the journal Royal Society Open Science.