Deception detection: psychologists try to learn how to spot a liar

Science News, July 31, 2004 by Carrie Lock

The differences between lying and truth telling were largely individual: Some suspects looked away more while lying than while telling the truth, and others increased their degree of eye contact, for example. The only general difference Vrij found between liars and truth tellers is that the liars blinked less frequently and paused longer while speaking.

In contrast to participants in the lab studies, the crime suspects didn't show any overall increase in speech disturbances or decrease in hand-and-arm movements. Because of the intense nature of a police interrogation, stressed truth tellers may display the same behaviors as liars do, Vrij speculates.

He is currently exploring lie detection from the side of the interviewer rather than the suspect. He showed 99 police officers tapes of real-life lies and truths and found that the officers were, at 65 percent accuracy, slightly better than lab-study participants at discerning the difference. But police are "still far away from perfect," Vrij points out.

He attributes the police officers slightly better performance primarily to the nature of the lies they hear during an interrogation. "More is at stake, and that gives the lies away more," he says.

Most recently, Vrij has tested whether the police officers' accuracy rates are consistent in multiple tests. In this study, 35 police officers took four tests derived from interviews of either liars or truth tellers, and 70 percent of the professionals' calls were correct.

Although the officers again outperformed participants in lab studies, no individual officer stood out. "Our early findings indicate that none was consistently good or consistently bad," Vrij says. "Nobody is 80 percent overall."

WIZARDS OF DETECTION Other researchers, however, present evidence that highly skilled human lie detectors do exist. The scientists have been trying to identify such people and figure out how they recognize lies.

In a now-famous study from more than a decade ago, about 500 Secret Service agents, federal polygraphers, and judges watched 10 1-minute video clips of female nurses describing the pleasant nature films they were supposedly watching as they spoke. Half the women were instead watching what Ekman calls "terribly gruesome" medical films. The legal-system professionals were asked to determine the truth by reading the women's faces, speech, and voices.

Ekman and his coauthor Maureen O'Sullivan of the University of San Francisco motivated the women to lie by telling them that because nurses shouldn't be bothered by gory images, their believability related to their future career success.

Most of the observers uncovered lies at only about the level of chance. One group, however, outperformed the others. The Secret Service group had a better-than-chance distribution, with nearly one-third of the agents getting 8 out of 10 determinations correct, the San Francisco psychologists reported in 1991.

O'Sullivan now says that her further studies of federal agents, forensic psychologists, and other groups of professionals indicate that a very small percentage of people are extremely good at spotting a phony. "We always found one or two people who were very good," she says.