CogniFit's Science blog: Can Your Brain Spot A Liar?

Can Your Brain Spot A Liar?

Our brain and our senses have a hard time to spot lies. An interesting study published in the journal Psychological Science in the Public Interest has shown that people or lies detectors cannot easily detect lies when observing someone’s non verbal behavior or simply listening to someone speech. Even modern lies detector still have problems to accurately detect lies.

The researchers explain this phenomenon with three majors reasons:
1) People have a lack of motivation to detect lies and therefore don’t actively look for it (they are not really interested or prefer to listen and accept what they are being told as it might be simpler).
2) Difficulties exist with lie detection such as the absence of cue (“the Pinocchio nose”).
3) Lie detectors don't always work properly when they are used because of the uniformity of their process.

For humans, what makes it difficult to know when someone is lying is principally that there are no external signs showing that the person is lying. You don’t actually see any external and visible indication. Also, because there are only small differences betweens liars and truth tellers, it is difficult for the brain to easily notice the discrepancy. Liars are actively trying to deceit you and usually they succeed in doing it.

For lies detectors, the main reason they don’t always catch liars is that they are looking and analyzing the wrong cues, placing too much importance on non-verbal factor and because they emphasize too much certain signs (such as nervousness or perspiration). They tend to neglect individual differences that could help detect a lie. They have a hard time to adapt to the person they are “interviewing” and understand the personal traits of the individual. The detectors are programmed with rules that could apply to the average of the population and don't know how to spot the nuances.

Still, it appears that lying is cognitively more difficult that telling the truth. The authors suggest therefore that one of the technique that could be used to spot lies would be to “impose a cognitive load”. By introducing a “mentally taxing” intervention that requires a higher degree of cognitive demand, the potential liar would have less brain resource at disposal to lie.

The authors recommend two ways to do this: 1) by asking the person to tell his/her story in reversed order and 2) by asking the person to speak while maintaining eye contact with the interviewer. Both technique demands a higher utilization of the person’s cognitive resources, making it more vulnerable to errors.

Future research around the brain and cognition will continue to develop our capacity to spot lies. Can you imagine a world where we always know when someone is lying?

It will be interesting to see how this will affect our society in the years to come, when liars won’t be able to lie anymore!