The physiological data collected during the course of a polygraph examination stems from the operations of the  sympathetic nervous system, which is a subset of the autonomic nervous system. The autonomic nervous system operates independently of any effort made by anyone. For example, you don’t have to think about making your heartbeat, and couldn’t affect it if you wanted to.  Same thing with breathing. It is something that we all do, and we really don’t have to think about it every much. Cardiovascular and respiratory operations in the human body continue to function on their own under the auspices of the autonomic nervous systems even when we are asleep.

 

Breathing is a good example of physiological data which we can consciously affect – to a point.  For example, we can breath quickly or slowly, or we can hold our breath. Indeed, if we are determined we can hold our breath until we lose consciousness, but then the autonomic nervous system intervenes and causes us to breath once again.  Efforts on the part of uncooperative or deceptive persons to manipulate a polygraph can be detected, identified, and thwarted by properly trained and competent examiners. There have been many who have tried to artificially impact the outcome of a polygraph examination by means of what are known as countermeasures, but the vast majority who attempt such countermeasures simply fail inasmuch as these techniques are widely recognized throughout the polygraph community.  An accuracy rate of more than 90% attests to the difficulty of attempting to “beat the test”.