science museum

Lie detectors

Lie detectors work by recording changes in heart rate, or in the sweatiness of palms - both of these increase when someone is telling a lie. However, a racing heart and sweaty palms may be caused by different reasons, which is why lie detectors are not totally reliable.

Man undergoing a polygraph lie-detector test.
Man undergoing a polygraph lie-detector test.
Richard T Nowitz/Science Photo Library

Science Museum Home Page Who am I? Science Museum Home Page