Do Polygraphs Work?
The polygraph, or so-called “lie detector” test, operates on the premise that emotions are accompanied by measurable physiological changes. When some people lie, they feel anxious, which causes changes in blood pressure, heart rate, breathing, and production of sweat. By monitoring these variables, the polygraph can theoretically detect when a person feels stressed from lying (APA, 2004). However, the polygraph is not as effective as Hollywood may lead you to believe. Research suggests that error rates may be anywhere from 25% to 75% (Saxe, 1994).

Guy Bell/Alamy