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Lie Detection Unplugged

Some people, from practiced detectives to brain-damaged aphasics, can spot a liar much better than you can. Here’s why.

By Cathryn Delude // Spring 2006
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Most people enjoy about the same odds of spotting a liar as they do guessing heads or tails. But a select few—from aphasics to ace detectives—excel at distinguishing truth from fiction as much as 90% of the time. What differentiates the perceptive from the gullible? Much has to do with the architecture of the brain, and damage to particular regions seems to enhance or hinder the ability to see through a lie. But motivation also matters.

In one study, people with aphasia proved to be naturals at spotting emotion-based lies, with a success rate of better than 70%. (Aphasia results from damage to the brain’s left hemisphere, which makes it difficult to understand or produce language.) Nancy Etcoff of the Massachusetts General Hospital, who collaborated on the study, speculates that losing verbal abilities allows nonverbal skills to flourish—like being able to notice suspicious microexpressions (the revealing grimaces, frowns and twitches that Paul Ekman, professor emeritus of psychology at the University of California at San Francisco, has cataloged) without being distracted by what someone says.

But while damage to the left hemisphere may sharpen lie detection skills, damage to the right could dull them, according to brain-imaging studies that Julian Paul Keenan of Montclair State University in New Jersey has done. Parts of the right brain, and the anterior cingulate gyrus, which spans both hemispheres, allow us to know our own thoughts and intuit others’ intentions. Without a fully functioning right brain, people can’t deceive—or detect deception.

Finally, whether your right or left hemisphere helps you flag liars may depend on the nature of their lies, suggests Maureen O’Sullivan of the University of San Francisco. She found that a good detective must call upon the left brain’s verbal acuity, asking the right questions and spotting inconsistent answers. But accomplished psychotherapists don’t so much need to determine the factual accuracy of a statement to understand patients’ thoughts and feelings. Being able to look beyond what patients say to grasp what they really mean requires the insights lent by the right brain.

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