Behavior: The Fine Art of Catching Liars

Psychologist Paul Ekman ran the film over and over until he found the clue. Mary, a housewife who had attempted suicide three times and had been confined to a mental institution, appeared chipper and confident onscreen as she asked - her doctor for a weekend pass. Her interview, secretly shot for research purposes, was so convincing that Mary got the pass, but she subsequently admitted that she had been lying and had wanted to get away for another suicide try. By slowing down the film, Ekman found that Mary's face had sagged into despair, a telltale "microexpression" that lasted only one twenty- fourth of a second. Later he found other quick movements of deceit: part of a hand shrug, the brief lift of a shoulder.

In his new book Telling Lies (W.W. Norton; $17.95), Ekman, 51, a professor of psychology at the University of California at San Francisco, says that catching liars is an art that anyone can learn: most duplicitous people unwittingly release a barrage of giveaway information during their deceptions. The key to judging sincerity is in paying close attention to the signals issuing from a talker's face, body and voice. In one of Ekman's experiments, all 50 members of a group of volunteers learned to pick up revealing microexpressions as brief as one twenty-fourth of a second. "Liars," he says, "usually do not monitor, control and disguise all of their behavior." Ekman's lessons come with one large caveat: even the best liar catchers cannot be right 100% of the time. The ear tugger, the evasive rambler and the fellow who refuses to look you in the eye may be lying, but they may instead be fidgety truth tellers who are afraid of being accused of deceit. The person who rubs his nose every 30 seconds may be dissembling, or he may simply be displaying a lifelong nervous habit. Diplomats, natural performers and pathological liars are often impossible to read. Says Ekman: "We live in a probabilistic world. You're only going to make an estimate." (Nazi Dictator Adolf Hitler, Ekman believes, was good at lying because of his ability to hide his emotions. British Prime Minister Neville Chamberlain, duped by Hitler at Munich in 1938, once wrote, "Here was a man who could be relied upon when he had given his word.")

Still, Ekman offers many useful guidelines for sorting out everyday liars. Among his tips:

-- A prolonged smile or look of amazement that lingers is probably false. Almost all authentic facial expressions fade after four or five seconds. In Ekman's theory, there are 18 kinds of authentic smiles.

-- The body gestures and facial expressions of liars are often out of sync. The person who bangs the table but then waits a split second to produce an angry face is probably faking.

| -- Crooked, or asymmetrical, facial expressions are usually deceitful (see box).

-- In 70% of people tested, the pitch of the voice rose slightly when they were upset, afraid or angry, a broad clue to the possibility that they were lying.