Catching A Liar
How do you know if someone is lying to you? Deception detection is an inexact science, but there can be some tell-tale signs, say Bella DePaulo of the University of California, Santa Barbara, and Wendy Morris of the University of Virginia in The Detection of Deception in Forensic Contexts, from Cambridge University Press.
Contrary to folklore, liars are not more fidgety, nor do they blink more or look less relaxed. Liars do tend to seem more nervous than truth-tellers, however, perhaps because their voices are pitched higher. There is also an association between lying and larger pupil size, a signal of tension and concentration.
The kind of lie determines the signals. When liars are highly motivated - when the stakes are high - they become unusually still and make notably less eye contact with listeners. When the lie is planned, deceivers start their answers more quickly than truthtellers. If taken by surprise, however, the liar takes longer to start answering questions, and they talk less.
The content of speech can be another tip-off. Liars seem more negative than truth-tellers - more complaining and less cooperative. They also tend to withhold information, either from guilt or to make it easier to get their stories straight, and to repeat words and phrases. "Liars' answers sound more discrepant and ambivalent; the structure of their stories is less logical," the researchers write.
It may even be possible to spot a liar if a written statement is all there is to go on. Content-based criteria analysis is a technique used by forensic scientists to systematically analyse witness statements to work out if t" are true or fabricated. The technique involves checking the statement for 19 criteria thought to be hallmarks of truthfulness. True statements are supposed to include more superfluous details, spontaneous self-corrections and speculation about other people's mental states. The truthful witness is also more likely to be self-deprecating and to make comments that go some way towards pardoning the alleged perpetrator.
The success rates reported for content-based criteria analysis seem to vary depending on the circumstances. But one small study of its use in testing teenagers' claims of school bullying found a success rate of 95 per cent. That compared with 55 per cent success for judgements made by the school's teachers.
Contrary to folklore, liars are not more fidgety, nor do they blink more or look less relaxed. Liars do tend to seem more nervous than truth-tellers, however, perhaps because their voices are pitched higher. There is also an association between lying and larger pupil size, a signal of tension and concentration.
The kind of lie determines the signals. When liars are highly motivated - when the stakes are high - they become unusually still and make notably less eye contact with listeners. When the lie is planned, deceivers start their answers more quickly than truthtellers. If taken by surprise, however, the liar takes longer to start answering questions, and they talk less.
The content of speech can be another tip-off. Liars seem more negative than truth-tellers - more complaining and less cooperative. They also tend to withhold information, either from guilt or to make it easier to get their stories straight, and to repeat words and phrases. "Liars' answers sound more discrepant and ambivalent; the structure of their stories is less logical," the researchers write.
It may even be possible to spot a liar if a written statement is all there is to go on. Content-based criteria analysis is a technique used by forensic scientists to systematically analyse witness statements to work out if t" are true or fabricated. The technique involves checking the statement for 19 criteria thought to be hallmarks of truthfulness. True statements are supposed to include more superfluous details, spontaneous self-corrections and speculation about other people's mental states. The truthful witness is also more likely to be self-deprecating and to make comments that go some way towards pardoning the alleged perpetrator.
The success rates reported for content-based criteria analysis seem to vary depending on the circumstances. But one small study of its use in testing teenagers' claims of school bullying found a success rate of 95 per cent. That compared with 55 per cent success for judgements made by the school's teachers.
posted by Scrup @ 10:09 PM
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