VANDERBILT HON 182 - Law and Lie Detection (7 pages)

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Law and Lie Detection



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Law and Lie Detection

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Pages:
7
School:
Vanderbilt University
Course:
Hon 182 - The Copernican Revolution

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Law and Lie Detection Polygraph http people howstuffworks com lie detector1 htm http people howstuffworks com lie detector3 htm Facts American Polygraph Research 98 reliability Analog polygraphs Digital polygraphs When you sit down in the chair for a polygraph exam several tubes and wires are connected to your body in specific locations to monitor your physiological activities Deceptive behavior is supposed to trigger certain physiological changes that can be detected by a polygraph and a trained examiner who is sometimes called a forensic psychophysiologist FP This examiner is looking for the amount of fluctuation in certain physiological activities Respiratory rate Two pneumographs rubber tubes filled with air are placed around the test subject s chest and abdomen When the chest or abdominal muscles expand the air inside the tubes is displaced In an analog polygraph the displaced air acts on a bellows an accordion like device that contracts when the tubes expand This bellows is attached to a mechanical arm which is connected to an ink filled pen that makes marks on the scrolling paper when the subject takes a breath A digital polygraph also uses the pneumographs but employs transducers to convert the energy of the displaced air into electronic signals Blood pressure heart rate A blood pressure cuff is placed around the subject s upper arm Tubing runs from the cuff to the polygraph As blood pumps through the arm it makes sound the changes in pressure caused by the sound displace the air in the tubes which are connected to a bellows which moves the pen Again in digital polygraphs these signals are converted into electrical signals by transducers Galvanic skin resistance GSR This is also called electro dermal activity and is basically a measure of the sweat on your fingertips The finger tips are one of the most porous areas on the body and so are a good place to look for sweat The idea is that we sweat more when we are placed under stress Fingerplates called



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