How Accurate Are Lie Detectors?
On One Hand: Not Very AccurateStandard lie detectors use a device called a polygraph that charts several physiological functions–heart rate, respiration, blood pressure and perspiration–looking for the increase in them that generally comes along with a lie. But since the experience of taking a lie detector test is stressful in itself, a nervous subject may trip the polygraph even if he is being truthful. And some people–sociopaths, to take an extreme example, or simply the well-prepared–will not experience any of the common physiological effects of a lie.On the Other: They Are Frequently UsedSome police investigations make use of the polygraph, and aspiring employees of sensitive government organizations like the FBI or CIA may take a polygraph as part of the application process. Polygraph advocates claim an accuracy rate of 90 percent.Bottom LineThe scientific community has long denounced polygraphs as “pseudoscience”, and in the United States, polygraph evidence is not admissible
