The Lie Detector

A lie detector, or polygraph, 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 lying can cause detectable changes in these bodily functions due to increased stress or anxiety. The polygraph records these responses on a graph, helping investigators assess whether someone might be deceptive. However, it does not directly detect lies; instead, it indicates physiological arousal, which can be caused by various factors. As a result, polygraphs are considered supplementary tools rather than definitive proof of truth or deception.