What Exactly is a Polygraph Test?
In tv shows and movies, polygraphs (or “lie detector tests”) are often painted as mechanisms by which a defendant “gets off” or proves his or her innocence. Polygraphs are machines that hook up to a person to measure their physiological indicators such as perspiration and heart rate. It was once thought that when a person tells a lie, their heart rate and blood pressure change to indicate so. However, what many people do not know, is that polygraph tests are generally unreliable (ie. there are “false positives” or negatives), and their use has decreased. For example, if a person is nervous simply by virtue of taking a lie detector test, their heart rate will increase regardless and their test results will be inconclusive, rather than “passing.” Polygraphs may also be fooled if one is just able to control their physiological responses.