In an age of marketing hyperbole and corporate mendacity, the idea of truth has become slippery. But maybe we just don’t know how to spot a falsehood. According to Dr. Paul Ekman, a professor of psychology at the University of California, the body is a lousy liar.

For the last 30-odd years, the good doctor has studied telling gestures and speech. He’s created a catalogue of involuntary actions of the face—twitches of musculature that reveal when a person is constructing or concealing information. Each motion—say a raised eyebrow or a flared nostril—is called an Action Unit. Analyze all of the Action Units and, although you might not know what your subject is hiding, you’re nearly certain to know whether they ’re hiding something.

Buffy Childerhose: So deception is written on the body. How visible and significant are these tells?
Dr. Paul Ekman: Pretty visible. There are some really obvious things, facial expressions and gestural slips, like slips of the tongue. In the case that I worked on of an embezzler, the only mistake he made in many, many, many hours of interviewing was that he made the tiniest little head shake no when he said yes. He was totally unaware of it—as we usually are of such things—but he totally betrayed what he was saying.

bc: Do you focus primarily on the face, or how important is body language?
pe: My primary scientific work was getting the definitive evidence on universals of facial expression. Most of our facial expressions are universal, most of our symbolic gestures are not. If you see a Saudi Arabian, you’d be able to read their facial expressions as easily as anyone else, but you’d have no idea what their gestures mean. But as we’re not decapitated heads with tongues, we need to consider those things. I spend almost as much time on body movement as I spend on the face.

bc: How accurate can you be?
pe: Actually, there is no sign of lying itself. There are only signs that people are thinking more than you might think they would need to about their answer. We are looking for a change in behaviour as a sign of deception. If behaviour changes with a particular topic, and then reverts back with another topic—that’s a good rule.

bc: Who can your system benefit—law enforcement officers and the like?
pe: All of us—whenever anything matters there are emotions involved. In any relationship that isn’t trivial, there are emotions that are occurring, and we’re all better off if we understand how others are feeling.

bc: I’m just imagining, if my father had been a little more, say, perspicacious, how much more difficult my teenage years might have been.
pe: I strive to not put my children in a position where they would need to lie to me. They each have curfews, and I heard one of them coming in, a couple hours late. Next morning, I resisted the temptation to ask, “What time did you come in?” I would instead say, “I heard you come in a couple of hours after your curfew. What happened that made it difficult for you to get home?” What I’m doing is twofold: one is don’t bother trying to lie, because I already know what happened, and two, I’m not furious, what I’m saying is I want to understand.

bc: Clearly, you’re fairly adept at catching liars—is this a social handicap?
pe: No, not at all. Sometimes people are a little self-conscious, when they find out what I do, but I tell them the bald-faced lie that I can’t really understand people better than anyone else unless I see them on videotape. That’s not true, but y’know, it just sort of breaks the ice.

Paul Ekman is the author of Telling Lies: Clues to Deceit in the Marketplace, Marriage and Politics. His new book, Emotions Revealed, is due out in spring 2003. Check out his website, www.paulekman.com.