Polygraph testing, commonly known as a lie detector test, measures physiological responses such as heart rate, blood pressure, and respiration while a person answers questions. The underlying theory is that deceptive answers may trigger noticeable changes in these bodily functions. During the test, a trained examiner asks a series of questions while monitoring the individual's physiological responses. The results are analyzed to determine whether the person is being truthful or deceptive. While polygraph testing is used in various fields, including law enforcement and employment screening, its accuracy and reliability are often debated among experts.