the telltale brain

If you’ve ever watched a police drama or a crime movie, you’ve probably seen someone hooked up to a polygraph machine, a device that’s used to test whether someone is telling the truth. The machine tracks and graphs body functions that have been linked to lying, such as changes in blood pressure and breathing. By looking at spikes in the resulting graphs, the test administrator can supposedly determine whether someone is lying when asked a specific question. Unfortunately, honest people can show body changes because they’re nervous about the test, and good liars can fool the exam. But Scott Faro of Temple University in Philadelphia, Pennsylvania may have come up with a better way to detect deception — by scanning a person’s brain.

Faro and his colleagues asked volunteers to shoot a toy gun and then lie about it. Other participants were told to tell the truth. The volunteers were questioned about their actions as they underwent brain scans as well as polygraph exams. The scans showed that different parts of the brain are active when telling a lie than when telling the truth. Also, more areas of the brain were active when the volunteer lied, implying that deception may take more brain effort. In Faro’s study, both tests could accurately distinguish lies from truthful answers. It’s still too early to know whether someone could beat the brain-scan test, but the results suggest that it may be beyond a person’s conscious control, bad news for good liars everywhere.

This article appeared in the April 2005 issue of the children’s science magazine Muse.
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