Chris Wanjek, of LiveScience, has a run-down on all the reasons why a polygraph test (aka the lie detector) is a really lousy way to get to the truth…but points out that people (in this case, congress) just can’t seem to believe that…
A polygraph not a lie detector; it never was. A polygraph detects physiological expressions associated with lying in some people, such as a racing heart and sweaty fingers. The determination of truth vs. falsehood is a subjective interpretation by the polygraph examiner.
Not surprisingly, the examiner is often wrong. The anxiety associated with “oh no, they will detect that I’m lying” is rather similar to “oh no, they’re going to think I’m lying when I’m not.”
At the bequest of the U.S. government, the National Academy of Sciences (an organization of some of the smartest scientists in America, no lie) conducted an extensive study of the polygraph in 2002 and concluded “polygraph tests can discriminate lying from truth telling at rates well above chance, though well below perfection.”
The Academy said the polygraph “rests on weak scientific underpinnings despite nearly a century of study.” The high incidence of false positives-a truthful response determined erroneously to be a lie-makes the polygraph useless, the Academy said.
So yeah…one should be particularly skeptical if someone offers to take a polygraph to prove their innocence. However, we might suggest looking into some pretty cool fMRI methods that show promise.
More from LiveScience.com
