The Other Polygraph
You’ve no doubt heard about the polygraph and its use as a lie detector. The homely box records physiological changes — such as heart rate and electrical skin conductance — that are indirect signatures of emotion. Because these biomarkers tend to change when people tell lies, criminal investigators have long used the polygraph as a crude tool for detecting deception.
But there’s a huge problem with the polygraph: it’s all-too-frequently wrong. Truth-tellers may show a strong physiological response to being questioned if they’re nervous or fearful, which they often are — particularly if the target of a hostile interrogation.
“You end up with a lot of false positives,” says John Meixner, a law clerk to Chief Judge Gerald Rosen of the United States District Court for the Eastern District of Michigan. The traditional polygraph suffers not only from false positives, but missed positives: With a bit of training, liars can pass the test by intentionally turning down their emotions.
Because of these considerable flaws, polygraph evidence is almost never allowed in court. But it’s still used routinely by federal law enforcement agencies, not only for screening accused criminals but potential new employees.
It turns out there’s a much more accurate way to root out deception: a 55-year-old method called the ‘concealed information test’. The CIT doesn’t try to compare biological responses to truth versus lies. Instead, it shows whether a person simply recognizes information that should only the culprit (or the police) could know.
Read more at...