What does a lie detector proof?

A lie detector, or polygraph, measures physiological responses such as heart rate, blood pressure, and respiration while a person answers questions. It is believed that deceptive answers may trigger noticeable changes in these responses. However, the accuracy and reliability of lie detectors are widely debated, as various factors can influence results, including anxiety and individual differences, making them more indicative of stress than truthfulness. Consequently, polygraph results are not universally accepted as definitive proof of lying.