The polygraph test: last resort of the accused and desperate. In 2009, cocktail waitress Rachel Uchitel told two tabloids she’d take a lie-detector test to disprove charges she had an affair with Tiger Woods. Earlier this year, Lindsay Lohan offered prosecutors the same deal after she pinched a $2500 necklace. Facing new allegations of sexual assault, Herman Cain wants in too. While one intrepid Atlanta P.I. has already proclaimed Cain’s innocence based on a voice test he conducted, the likelihood we’ll get a dramatic public polygraph press conference (a la boxing match weigh-in or Maury Povich DNA test reveal) remains slim. Even so, could we have trusted the accuracy of Herman Cain’s polygraph test?
Hardly, according to a 1986 paper from The Lancet. Using previous polygraph research conducted on lying criminals, the researchers found that the device typically accused nine of ten people falsely, given a sample size of test takers among whom five percent were actually "guilty." Conversely, only two percent of liars went undetected. In other words, if Herman Cain takes a poly and fails, there’s a good chance he's innocent. If he passes, he’s still probably innocent. All of which explains his desire to take a polygraph test: heads he wins, tails the results are untrustworthy anyways. A more recent study details researchers’ ambivalence about even measuring the scientific validity of polygraph tests, one of them noting that in controlled lab experiments polygraph users “are not threatened by severe consequences of failing a test” and that using real criminals’ testimony is similarly dicey given the lack of “conclusive exonerating or incriminating evidence that can corroborate test outcome.” The most convincing argument against using polygraphs comes from the initial Lancet study: “There is no rational scientific basis for any machine to detect liars’ consistency, since there is no known consistent physiological response unique to the cognitive state of lying.” Except asking to take a polygraph test in the first place.