The Pseudoscience of Lie Detectors
More commonly known as the lie detector, the polygraph is a device that measures the changes in our nervous systems, detecting and recording heart rate, respiration, sweating and blood pressure. It allegedly operates on the premise that due to anxiety and fear, people produce involuntary physiological responses when they lie. Some claim that polygraph testing is up to 96% accurate, while others claim 50%, but it’s likely somewhere in between. Polygraphs only detect physiological responses, which don’t directly translate to proof of lying—some guilty people can remain completely calm while lying, while innocent people might produce ‘guilty’ responses. Polygraphers ask control questions to determine normal responses and balance this, but the tests are therefore inherently subjective because a human interprets the results. The ‘base rate fallacy’ also causes considerable problems, involving ignoring statistical information and not taking into account the frequency of what’s being tested for. For example: using the 96% accuracy rate, suppose that statistically, 1 in 10,000 people are terrorists—but if 10,000 people are randomly polygraphed, 1 terrorist and 400 false positives will be turned up, so the 96% accuracy isn’t useful or meaningful. Polygraphs are used as a tool for psychological bullying rather than accuracy, intimidating suspects into confessing—and they are, therefore, a pseudoscience.