A standard polygraph instrument records changes in blood pressure, pulse rate, pulse strength, galvanic skin reflex (sweat gland activity) and upper and lower breathing patterns. It does not matter if the examinee is “nervous” during the testing process – that is to be expected. The polygraph records significant changes from the subject’s “norm” when specific questions are asked. A person intending deception to a particular question will activate his/her Sympathetic Nervous System as a “self defense” mechanism when that question is asked on the test. The SNS activation will cause recognizable changes in one or more of the physical responses.
