The Truth About Polygraphs: The Science and Limitations of Lie Detectors

Polygraphs, also known as lie detectors, were first used in police interrogations in 1924. They operate on the theory that lying triggers the sympathetic nervous system, causing measurable physiological responses such as increased heart rate, breathing, blood pressure, and perspiration. Devices are attached to the body to measure these responses. The Control Question Test (CQT) is a common method used, comparing responses to control questions with those to relevant questions. However, polygraphs are not foolproof, as there's no unique pattern to lying, and their accuracy is about 75%. Ultimately, guilt is best proven through admission or clear evidence.

What physiological responses does a polygraph measure to detect lies?

• Heart rate, breathing, blood pressure, and perspiration

• Brain waves and muscle tension

• Eye movement and voice pitch

• Body temperature and pupil dilation

What is the purpose of the Control Question Test in a polygraph examination?

• To compare responses to control and relevant questions

• To measure the interviewee's intelligence

• To determine the interviewee's emotional state

• To confuse the interviewee

Which of the following is a control question example in a polygraph test?

• What is your name?

• Where were you last night?

• Have you ever betrayed someone who trusted you?

• Did you commit the crime?

What is the accuracy rate of polygraphs according to studies?

• 50%

• 60%

• 75%

• 90%

What is considered the only reliable way to prove someone's guilt?

• Body language analysis

• Eyewitness testimony

• Person's own admission or clear evidence

• Polygraph test results