PSYC 3020 Chapter 4: CHAPTER 4.docx
30 Mar 2012
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Document Summary
Underlying principle of polygraph: deception is associated with physiological change. The origins of modern polygraph date from 1917 when william marston developed a systolic blood pressure test and attempted to use this physiological response as evidence for a person"s innocence. Polygraph: a device for recording an individual"s autonomic nervous system. Measurement devices are attached to upper chest and abdomen to measure breathing. The amount of sweat on the skin is measured by attaching electrodes to the fingertips. Sweat changes the conductance of the skin, which is known as the galvanic skin response. Finally, heart rate is measured by a partially inflated blood pressure cuff attached to an arm. Each of these measures is amplified and can be printed out on paper or stored in a computer to be analyzed. Polygraph is used to measure a person"s physiological responses to questions asked by an examiner. In canada, the police often use them to help in their criminal investigations.
