With some careful observation--and a little help from new software--anyone can learn to be a lie detector

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"You can tell a lie but you will give yourself away. Your heart will race. Your skin will sweat ... I will know. I am the lie detector." Thus began each episode of Lie Detector, a TV show -----(1)------ . Participants ----- (2) ----sat on a couch and were quizzed by the program's host. A frequent topic of discussion was one guest's suspicion that his or her partner had been unfaithful. The person suspected of infidelity denied it, of course, and the object of the show was to find out ----- (3) ----- whether that person was telling the truth.


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Knowing how to catch deceit can be just as important a survival skill as knowing how to tell a lie and get away with it. A person able to spot falsehood quickly is unlikely to be swindled ----- (4) -----. By closely observing facial expressions, body language and tone of voice, ----- (5) ----- . Researchers are even programming computers--like those used on Lie Detector--to get at the truth by analyzing the same physical cues available to the naked eye and ear. "With the proper training, many people can learn to reliably detect lies," says Paul Ekman, professor of psychology at the University of California, San Francisco, ----- (6) ----- .

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In order to know what kind of lies work best, successful liars need to accurately assess other people's emotional states. Ekman's research shows that this same emotional intelligence is essential for good lie detectors, too. The emotional state ----- (7) -----, the conflict most liars feel between the truth and what they actually say and do.
Even high-tech lie detectors don't detect lies as such; they merely detect the physical cues of emotions. Polygraphs, for instance, measure respiration, heart rate and skin conductivity, which tend to increase when people are nervous ----- (8) ----- . Nervous people typically perspire, and the salts contained in perspiration conduct electricity. That's why a sudden leap in skin conductivity indicates nervousness--about getting caught, perhaps?--which might, in turn, suggest that someone is being economical with the truth. On the other hand, it might also mean that the lights in the television studio are too hot ----- (9) ----- . "Good lie detectors don't rely on a single sign," Ekman says, "but interpret clusters of verbal and nonverbal clues that suggest someone might be lying."