Psychology and Law Enforcement - Using Psychology to Find Liars
October 29, 2004
Telling a little white lie might soothe ruffled social feathers, but covering
up a murder plot or withholding information on terrorist cells can devastate
individuals and society at large. Yet detecting deception often stumps the most
experienced police officers, judges, customs officials and other forensic
professionals. Psychologists are lending their expertise to help law enforcement
find out who’s lying.
Spotting the sneaks can be tough. Polygraph tests- so-called "lie detectors"--are considered unreliable. That's why psychologists have been cataloging clues to deception--such as facial expressions, body language and word choice--to help hook the dishonest. From this research, psychologists are developing new detection tools such as software to analyze facial expressions and writing style.
They're also training law-enforcement experts, from airport security guards to counter-terrorism agents, foreign-service officers and police interrogators, including officials from the CIA, FBI and other such federal agencies.
Knowing when someone is lying isn’t an exact science. But some
psychologists say that people who lie have slightly enlarged pupils, indicating
tension and concentration. And people who talk with liars, say the liars seem
more nervous than truth-tellers, maybe because their voices are pitched higher.
Liars also are more likely than truth-tellers to press their lips together. But,
despite what many people believe, liars don’t fidget more, blink more, or look
more tense that those telling the truth. Only when liars have a lot to lose –
like their spouse, money or their reputation -- do they seem unusually still and
make notably less eye contact with listeners.
Facial expressions aren't the only clue. Because deception is a social act involving language, researchers are also studying what liars say and write.
Liars take longer to start answering questions than truth-tellers--but when they have time to plan, liars actually start their answers more quickly than truth-tellers. And they talk less. On the whole, to other people, liars seem more negative--more nervous and complaining, and less cooperative--than truth-tellers.
One psychologist has developed computer software that looks at what a person writes to help law enforcement predict whether someone is lying. The software looks at the fact that liars avoid first-person pronouns such as “my” or “mine;” that they use more negative emotion words such as “hate” and “sad;” and use fewer words like “except,” “but” or “nor” that show they can tell the difference between what they did and what they did not do. The software developers say it has a 67% accuracy rate.
Computer programs aren't the only methods of detecting lies. Some scientists believe that people--such as law-enforcement officers--can be trained to recognize liars through behavioral clues. And psychologists are helping train law enforcement officers as well as observing interrogations themselves to give law enforcement the benefit of what psychology knows about liars.
They are teaching law enforcement to look for behavioral clues into lying such as thinking too much when a reply should not require thought, or emotions that don't fit what is being spoken.
In the end, psychologists say that detecting deception is all about honesty -- it's much harder to find the truth than to find a lie. A good lie-catcher is good at identifying truthfulness.
Adapted from the APA Monitor on Psychology, July/August 2004, Vol. 35, No. 7
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