The Lie Detector Machine - What Is It?

By Fabiola Castillo

Measuring the trustworthiness of an individual is something that perceptive interrogators do to get at the truth of a person's statements.

Kinesiology, the study of body language, speaks louder than words to those who know how to "read" body language. A person who is lying to you rarely makes eye contact, covers his mouth, scratches his nose, rubs the back of his neck, clears his throat repeatedly, blinks his eyes, drinks water excessively, and fidgets with his feet. He does this at the same time while his voice trembles, his pores sweat, and his face blushes. You may have seen these activities when former President Bill Clinton was the subject of a videotaped deposition for his involvement in the White House sex scandal in the late 90's.

These physiological effects are always accompanied by the anxiety involved in lying. Such physiological effects are not always visible but can be measurable using instrumentation that detects changes in a person's physiology.

What is a polygraph machine?

A polygraph machine, also known as a lie detector, refers to the instrument that measures and records the changes in several physiological processes.

Polygraph literally means "many writings." As the name implies, the polygraph is a conglomerate of several instruments used to measure several distinct processes that include:

• A cardiograph-a machine that measures pulse rate and blood pressure.
• A galvanograph-a machine that measures differences in the electrical resistance of the skin. Sweating increases the electrical conductivity in the skin due to electrolyte concentration in sweat.
• A pneumograph-a machine that measures the rate and depth of breathing.

Some polygraphs involve another instrument known as a plethysmograph. A plethysmograph is an instrument that attaches to the index finger and is used to measure oxygen concentration and peripheral blood flow.

Not all polygraph examinations are conclusive. There are some faults involved in administering a polygraph. For one, not everybody displays the same generalized physiological effects that liars do. Alcohol, drugs, legal or illegal, and other medications can affect a person's physiology that would nullify the results of a polygraph. Previous surgeries or illnesses can affect the results of a polygraph not to mention the examiner's competence in the use of the polygraph machine. Also, somebody who is an expert in lying can nullify the results of a polygraph exam. Actors and actresses do this for a living. In essence they, are professional "liars."

For these reasons, results of a polygraph examination are inadmissible in many court systems. They are only used to steer law enforcement in the right direction when investigating a crime.

Fabiola Castillo is an online marketer for the website NinjaCOPS SuperStore. This virtual store specializes in crime prevention tools where you can buy cheap stun guns, kubaton keychains, hidden video spy surveillance cameras, nunchaku training videos, civilian Tasers, expandable steel batons, and many other personal safety products.

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