Stroke victims are best judges of a liar

People who lose their language ability because of brain damage develop an extraordinary gift for spotting liars, scientists have discovered.

People who lose their language ability because of brain damage develop an extraordinary gift for spotting liars, scientists have discovered.

Stroke victims who have suffered damage to the brain's language centres learn how to detect the subtle facial expressions that can indicate when a person is lying. Tests on a group of aphasics - people who cannot converse after brain damage - showed they could detect liars nearly threequarters of the time, compared with a 50:50 success rate for undamaged people. One aphasic who had recently suffered brain damage performed no better than healthy subjects, indicating that the ability is learnt through experience.

A team led by Nancy Etcoff, a psychologist at Massachusetts General Hospital in Boston, report in the journal Nature that the study was the first to prove brain-damaged people were superior at spotting deceitfulness. The scientists said: "Aphasics were significantly better at detecting lies about emotion than people with no language impairment, suggesting that loss of language skills may be associated with a superior ability to detect the truth."

The Boston team suggests loss of language results in the growth of "compensatory skills" that allow aphasics to recognise better the subtle signs and cues of non-verbal behaviour, such as avoiding eye contact when someone is lying.

Dr Etcoff said: "One question that may arise when considering these results is whether the patients were better at detecting lies or at detecting emotional states. What they do seem to be more sensitive to are nuances in facial expression that reveal a disconnection between what someone is trying to express and what they really are feeling."