Liars are exposed by blinking

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By Lucy Cockcroft
Last Updated: 12:01am BST 20/08/2008


The best way to spot a liar is to look them in the eyes, according to scientists who say the number of times a person blinks will show if they are speaking the truth.

Liars blink less frequently than normal during the lie, and then speed up to around eight times faster than usual afterwards.

The findings, reported in the Journal of Non-verbal Behaviour, means that blink rates could soon be used by professionals, such as the police and security forces, to tell when someone is being duplicitous.

Dr Sharon Leal, co-author of the study at Portsmouth University, said: "It is striking what different patterns in eye blinks emerged for liars and truth tellers.

"Such striking differences in behaviour between liars and truth tellers are rarely seen in deception research."

Researchers studied a group of volunteers as they went about their normal business for ten minutes. A second group were asked to steal an exam paper from an office, then to deny having taken it.

The groups were then asked each to recall exactly what they had been doing.

During the interview their blink rates, which had all been the same at the start, were monitored with electrodes placed above and below and at the sides of the eyes to monitor all movements.

Results show that when the questions were being asked and the answers given, the blink rate in the liars went down. In contrast the truthful group's rate went up, though this could have been down to test anxiety.

Afterwards, the blink rate of the liars increased rapidly, while that of the truth tellers remained the same.

Researchers believe the increased effort involved in telling fibs could be the reason why liars do not blink during the act of lying.

Dr Leal said: "Liars must need to make up their stories and must monitor their fabrication so that they are plausible and adhere to everything the observer knows or might find out.

"In addition, liars must remember their earlier statements, so that they appear consistent when re-telling their story, and know what they told to whom. Liars will be more inclined than truth tellers to monitor and control their demeanour so they will appear honest.

"The reasons why there is a flurry of blinks after the lie is not really clear. It may be that this flurry is a kind of safety valve, like a release of energy after the tension of lying."



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Well this study was done among "normal" students. I doubt if the results could be so clear with "professional" members of the criminal class, lawyers, and sociopaths. --Ed