Polygraph (lie detector)

A polygraph, or lie detector, 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 lying, these physical responses may change due to stress or nervousness. The device records these changes, which are then analyzed to assess truthfulness. However, it doesn't directly detect lies; it detects physiological reactions that could indicate deception, but various factors can influence results. Therefore, polygraphs are considered tools to support investigations rather than definitive proof of truth or deception.