A lie detector, also known as a polygraph, is a device that is designed to measure physiological responses to questions in order to determine whether a person is telling the truth. Polygraphs are often used in criminal investigations and other legal proceedings in an attempt to obtain information or determine the veracity of a witness or suspect.
During a polygraph test, a person is attached to sensors that measure various physiological responses, such as blood pressure, pulse, respiration, and skin conductivity. The person is then asked a series of questions, and the polygraph measures their physiological responses to these questions. The theory behind the polygraph is that people who are lying will exhibit certain changes in their physiological responses that can be detected by the sensors.
Polygraph tests are controversial and their accuracy is widely debated. Some research has suggested that polygraphs may be able to accurately detect deception in some cases, but other studies have found that they are prone to producing false positives or false negatives. In addition, the results of polygraph tests are generally not admissible as evidence in court due to concerns about their reliability.