About Lie Detector Tests

Lie detector tests are used to determine whether a person is telling the truth about a particular subject. Various forms of lie detection exist, ranging from polygraph tests, voice stress analysis and cognitive chronology. Each test uses scientific method and psycho-physiology. Lie detectors such as the polygraph are admissible in court in some states in the United States.

Function

The premise behind most lie detector tests is to find truth via reflexes of the brain and body. The most popular lie detector is the polygraph. It records and measures the different physiological responses of the subject --like alterations in blood pressure, respiration, skin conductivity and pulse. Questions that provoke major changes in the subject's sympathetic nervous system are highlighted.

Type

The United States government uses this kind of polygraph examination (called a psycho-physiological detection of deception) for interrogating suspected criminals and spies. VSA (voice stress analysis) is another psycho-physiological lie detection test. In VSA, the voice of the subject is monitored for stress responses that may result from lying. In addition to the use of lie detector tests on suspected criminals, some television shows have popularized the polygraph as a way to catch a spouse or lover who is cheating. Private employers in the U.S. are prohibited by law from using lie detector tests before and during employment. However, government employees can be tested.

History of

The first lie detectors tried to highlight the so-called physical side effects of lying. Tribes in ancient West Africa would have groups of people pass an egg between each other. The one to break the egg was deemed the liar because nervousness was a quality associated with guilt. Toward the end of the 19th century, law officials used to measure the blood pressure of suspected criminals. William Marston, considered the "father of the polygraph," published The Lie Detector Test in 1938 to advocate its use in America's judicial system. The first polygraphs used analog technology. Most polygraphs are now computerized. The procedure and accuracy of the polygraph test is relatively identical for both analog and computerized tests.

Features

After being attached to the lie detector machine through a series of wires, the subject is given a preliminary examination so that the interrogators can build a foundation of control questions for the test. The success of the test depends on the subject's psychological mindset. If the subject believes in the effectiveness of the lie detector, he is more susceptible. Interrogators have developed keen ways of "influencing" subjects into believing the accuracy of the lie detectors. Many of these techniques have received criticism because some use intimidation to conjure nervous responses.

Misconceptions

The greatest misconception of the polygraph is that it's 100 percent accurate. Its developers and law officials often claim that it is between 90 percent and 95 pcercent accurate. However, a survey of psychologists taken in 1997 described the polygraph as a little over 60 percent accurate. The polygraph has had little success in exposing spies (like Aldrich Ames, Karl Koecher, Ann Belen Montes and Leandro Argoncillo), and is known for occasionally leading to the convictions of innocent people.

Resources

• Find out more about the history of the polygraph.
• Learn about the Employee Polygraph Protection Act.