Culture and Society

What does a polygraph machine measure to detect lies?
Answered by Discovery Channel
  • Discovery Channel

    Discovery Channel

  1. A polygraph machine is also called a lie detector test, though even its proponents admit that it cannot actually detect lies. Instead, the machine monitors the physical reactions interviewees have when they are asked specific sets of questions. The machine is composed of devices that detect and measure blood pressure, heart rate, electro-dermal activity and rate of respiration. An examiner will conduct an interview with someone while the polygraph records these physiological responses to each question. The examiner's hope is that analyzing patterns in this data will be able to show whether the interviewee is practicing deception.

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