How a Polygraph Works

There isn't even agreement among believers how the polygraph works. In fact, from what we have seen on previous pages (see the whole list on the homepage), it appears that is doesn't work. But there are three common theories about why it should work.

Sensitive Subjects

The first is that a subject reacts when questions strike sensitive areas, whether he is telling the truth or not. Of course there is a porblem with this theory, at least in terms of what it suggests about the accuracy of the polygraph. It seems to indicate that your nervousness (natural under the circumstances, right?) might be taken as dishonesty -- not a pleasant thought.

Mental Conflict

The second theory is the theory of conflict. It supposes that a measurable physiologic disturbance takes place when a subject is caught between a habitual inclination to tell the truth and a strong desire not to admit to certain actions of facts. Some researchers think that if this concept is valid, it is only when conflict is intense. Thus, questions where you are instructed to lie may not yield a large response, making them less useful for comparing later responses to.

Then there is the question of what happens when there is no "habitual inclination to tell the truth." Presumably then there is no conflict. Habitual liars may be measured as honest in this case.

Threat of Punishment

The most accepted theory is the threat-of-punishment theory. It says that a large physiologic response accompanies lying because a subject fears consequences for failing to deceive the operator. In other words, a subjects own fear of failing is what causes the response.

The problem that many researchers note is that one who does not fear the results of his failure should not produce measurable responses. If this is how a polygraph works, sociopaths might lie without any problem.

...the use of this highly flawed instrument should be radically curtailed. - Former CIA Director R. James Woolsey

Continues here... Passing a Polygraph

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