NCPA - National Center for Policy Analysis

Brain Scanner May Be A Better Lie Detector

November 13, 2001

It is common knowledge that polygraph tests are not completely reliable in detecting when a subject is not telling the truth. But scientists at the University of Pennsylvania say brain waves offer much greater promise of uncovering deceptions.

  • Unlike conventional polygraphs -- which assume that liars are anxious and that their 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.
  • A neural network is engaged when someone tries to deceive.
  • Scientists say defining deception is complicated because there are so many components to lying -- including deception, exaggeration, rationalization and imagination.
  • Researchers predict that it will take some time before such brain scans move from the laboratory to forensic settings.

That's because the technique is expensive and complicated. Also, a laboratory setting is different from a prison or courtroom -- and surroundings can alter results.

Source: Shankar Vedantam, "The Polygraph Test Meets Its Match," Washington Post, November 12, 2001.


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