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Monday, 12 November, 2001, 16:18 GMT
Your cheating brain
Brain scan, BBC
Secrets and lies: Brain waves may give them away
Brain scans can detect when someone is lying, according to scientists in the United States.

Tests revealed a distinctive pattern of brain activity when volunteers cheated during a card game.

University of Pennsylvania experts say the method could be superior to existing lie-detection systems.

But they say much more work needs to be done before the technique could be used in criminal investigations.

Dr Daniel Langleben told the BBC: "There are differences in brain activity during lie responses versus truth responses.

"However, I would be very cautious about postulating at this time that this could and will be used for criminal investigations."

'Guilty knowledge'

The evidence comes from a pilot study in which 18 volunteers took a "guilty knowledge" test while their brains were being scanned.

Each individual was given an envelope containing a five of clubs playing card. They were told to look at the card and then hide it.

Participants were then randomly shown playing cards. If the five of clubs card appeared, they were told to deny having it.

Several parts of the brain that are important in how humans pay attention, and monitor and control error, were more active when lies were being told.

The new research uses a brain scanning technique known as functional Magnetic Resonance Imaging (fMRI).

Body reaction

Scientists say the scanning method is potentially more accurate than the current lie-detection technique, known as polygraphy.

This registers certain physiological reactions associated with nervousness, including breathing rate, pulse, blood pressure and perspiration.

Critics say polygraphy is not always reliable as some people manage to fool the system.

Polygraphic evidence is not admissible in British courts.

Dr Daniel Langleben
The brain can betray a liar
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