"Each of us, at least once in a life, has asked themselves: 'Am I being lied to?' or 'How do I say a lie and get away with it?' Trying to find an answer to the latter, one may come up with all kinds of gimmicks and twists. Answering the first question is way more complicated. Polygraph, or 'lie detector' as journalists aptly dubbed it in the 1920s, was designed to detect and record the deception. The theory is that when a person lies, the lying causes a certain amount of stress that produces changes in several involuntary physiological reactions.

A series of different sensors are attached to the body, and as the polygraph measures changes in breathing, blood pressure, pulse and perspiration, pens record the data on graph paper. During a lie detector test, the operator asks a series of questions that set the pattern of how an individual responds when giving true and false answers. Then the actual questions are asked, mixed in with filler questions.

An earlier and less successful lie detector or polygraph machine was invented by James Mackenzie in 1902. However, the modern polygraph machine was invented by John Larson in 1921. John Larson, a University of California medical student, invented the modern lie detector (polygraph) in 1921.

At the federal level alone, the polygraph is used extensively in counter-intelligence, counter-terrorism, and counter-narcotics programs in addition to criminal investigations, intelligence operations, presidential protection and nuclear materials containment. There are at least 68 countries world wide where the polygraph is used for similar applications. In the private sector, polygraph is used extensively by individuals, families, therapists, attorneys, courts, business and many other entities.