How does a polygraph work?
The Polygraph records physiological changes that occur in the human body. These changes are evaluated based upon changes that occur when questions are asked. Most of us can remember a time when we lied to our parents or other significant person. We could feel the changes in our bodies. Often we could feel our heart racing, palms sweating, and other symptoms of apprehension. When we evaluate the polygraph charts, we can see up to 32 different physiological changes indicative of lying.
Prior to a polygraph examination getting underway, the examiner will fasten various painless components to and around the examinee’s body, thereby connecting him or her to the polygraph instrument. These components are equipped with sensors that serve to collect, measure and record, onto polygraph charts, the examinee’s physiological data obtained from three major systems of the body — i.e., i) the cardiovascular system (heart rate, blood pressure, blood volume); ii) the respiratory system (breathing patterns); and iii) the electrodermal system (sweat gland activity) — as he or she answers a series of questions pertaining to a specific issue during the course of the polygraph examination.
It is important to understand what a polygraph examination entails. A polygraph instrument will collect physiological data from at least three systems in the human body. Convoluted rubber tubes that are placed over the examinee’s chest and abdominal area will record respiratory activity. Two small metal plates, attached to the fingers, will record sweat gland activity, and a blood pressure cuff, or similar device will record cardiovascular activity.
