Truth Found in Liars’ Body Cues, Voices

People who tell lies apparently can disguise the deceit on their faces, but their voices and body language are dead giveaways, a scientist says.

“The face is not a reliable indicator of deceit,” USC communications expert Michael J. Cody said. “You can’t assume a liar will avoid eye contact, show fear of disclosure in his expression, or otherwise ‘leak’ facial cues to deception.

“Liars are just as likely as truth-tellers to look you straight in the eye.”

Cody, who studies nonverbal communication, described the face as the most expressive part of the body. Because of that, he said, it is the easiest to control.

Building Themselves Up

The USC studies of liars center on “the braggadocios”--liars who build themselves up by exaggerating anything from ancestry to where and how they spent a vacation.

Cody said their changes in posture, shifting and shrugging, moving legs and feet or making unintentional hand-to-body movements are the real clues to deception.

So is voice modulation.

“The pitch of the voice always goes up during a lie, and the pupils dilate,” he said, pointing out that the major physical cues can differ between children and adults.

“Children blink their eyes more and have an even higher pitch in voice,” he explained. “Children have to learn how to lie and never are very good liars before the age of 9.”

Hard to Detect

Cody and his team conducted a series of studies to determine if people untrained in nonverbal communications could tell when someone was telling a lie.

Results showed that the untrained were accurate only 45% to 60% of the time in detecting deception of strangers on videotape.

Cody said his research also shows that reliable detection of deception depends on knowing more than one signal of deceit.

“Very often lies are told off the top of the head and you can catch a person in a lie when they are unable to generate much detail about whatever they are talking about,” he said.

“Liars tend to have what I call ‘ah’ errors, and are more likely to have silence pauses and hesitations in speech. They say ‘you know’ and ‘ah’ a lot to take up time while they think of the rest of the lie.”