Polygraph

A polygraph, commonly called a lie detector, is a device that measures physiological responses—such as heart rate, blood pressure, respiration, and skin conductivity—while a person answers questions. The idea is that when someone is deceptive, these responses may change due to stress or anxiety. Although it doesn’t directly detect lies, the polygraph data can provide indications of deception, which experts then analyze. Polygraph results are used in criminal investigations, security screenings, and some research, but their accuracy and reliability are debated, and they are not universally accepted as conclusive evidence of truth or lies.