Accuracy demonstrations, threat, and the detection of deception: cardiovascular, electrodermal, and pupillary measures.

Subjects, half of whom committed a mock crime, were examined with both Control Question and Guilty Knowledge tests in an attempt to detect guilt or innocence. Skin resistance, heart rate, and pupil size were the physiological measures employed. Prior to the polygraph test the effectiveness of the physiological detection apparatus was demonstrated to each suhject. They were led to helieve they had been detected in either none, one, two or three of three trials in this demonstration. Subsequent detectability of subjects varied as a result of the manipulation with the Control Question test such that detectability increased as the level of demonstrated effectiveness increased. Results with the Guilty Knowiedge test were less clear. Another manipulation, threat of punishment, did not affect detection results but did alter heart rate change such that those threatened, whether guilty or innocent, received rank scores more in the guilt)’direction than those not threatened. Skin resistance was the most efficacious measure in both tests while pupil and heart measures varied in detection accuracy depending on the test employed.