“The Polygraph Test Meets Its Match: Researchers Find Brain Scans Can Be Powerful Tool in Detecting Lies”

Washington Post correspondent Shankar Vedantam reports in this page A02 article. Excerpt:

Telling a lie produces telltale changes in the brain, researchers announced yesterday at a neuroscience conference in San Diego.

Brain scans of volunteers asked to tell lies showed changes as the subjects tried to suppress what they knew was true. The result might eventually form the basis of highly accurate lie detector tests, scientists said.

Unlike conventional polygraphs, which assume that liars are anxious and that such anxiety causes measurable changes in skin and blood pressure, brain scans offer even coldblooded liars little opportunity to cheat because people cannot mask the mental processes responsible for lying.

“We see that a neural network is engaged when someone tries to deceive,” said Ruben Gur, a professor of neuropsychology at the University of Pennsylvania, where the research was conducted. “The components of that network are both the tendency to suppress telling the truth and the emotional response involved with the act of deception.”

“A procedure like this is very likely in the future for lie detection,” he said. Compared with conventional polygraph tests, Gur said, the brain scans “can be much more powerful.”

That is because skilled liars show less anxiety than novices and can sometimes pass polygraph tests, while truthful people can be intimidated into showing anxiety and be branded as liars. There are also physiological differences between people that can lead to polygraph unreliability.

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