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A polygraph (also known as Lie Detector) is a scientific diagnostic instrument that is used by a polygraph examiner to administer a polygraph examination for the purpose of verifying the truthfulness of a person’s statement regarding a specific issue. It monitors and records various manifestations of the Sympathetic and Parasympathetic Nervous Systems while a series of carefully designed questions is asked of the person who is attached to the instrument.

The polygraph instrument measures changes in blood pressure, pulse rate, electro-dermal activity, and respiration, and may include additional components as well, such as blood volume monitors and motion sensors. The term “polygraph” comes from the Greek words poly (many) and graph (writing) ‘ “many writings”. The name refers to the manner in which selected physiological activities are simultaneously collected, measured and recorded.
Generally, when a validated technique is used for specific issue test, the average accuracy of the polygraph will exceed 90%. However, the accuracy of a polygraph depends heavily on the following:

1. The specific technique used by the examiner (see Validated Testing Technique)

2. The examiner’s primary and continuing training (see How to Select an Examiner)

3. The number of relevant questions asked. In general, the more relevant questions asked the less accurate the results will be. Using only one relevant question will produce the highest level of accuracy that can be achieved. Most of the current research on polygraph is contingent upon the use of a “Specific Issue” format (one relevant question). Adding even one question to a specific issue test doubles the error rate.

4. Proper question design. Questions must be formulated correctly (see “Rules” below)

5. The American Polygraph Association has a compendium of research studies available on the validity and reliability of polygraph testing. The 80 research projects published by the APA since 1980 involved 6,380 polygraph examinations or sets of charts from examinations. Researchers conducted 12 studies of the validity of field examinations, following 2,174 field examinations, providing an average accuracy of 98%. Researchers conducted 11 studies involving the reliability of independent analyses of 1,609 sets of charts from field examinations confirmed by independent evidence, providing an average accuracy of 92%. Researchers conducted 41 studies involving the accuracy of 1,787 laboratory simulations of polygraph examinations, producing an average accuracy of 80%. Researchers conducted 16 studies involving the reliability of independent analyses of 810 sets of charts from laboratory simulations producing an average accuracy of 81%. The average accuracy for all 6,380 exams is 88%.

6. New industry standards require that a particular technique be at least 90% accurate (in specific issue testing) for that technique to be “validated.” It is important that the examiner uses a validated polygraph technique.

7. The actual make and model of polygraph instrument used is not nearly as important as the above-noted elements. A good examiner can provide reliable polygraph services using any calibrated polygraph instrument.
A validated testing technique is one that has been validated by the American Polygraph Association, through research, to achieve a minimum level of accuracy (90% for specific issue tests, 80% for multiple issue tests). Other techniques are less accurate and are not supported by scientific research.

Although very little activity and reaction occur in the brain when we lie, every human being has a self-defense mechanism that is activated whenever we are threatened or placed in danger. For example, if you are walking along a path and come across a poisonous snake, your brain will have a reaction to that snake because you realize it could hurt you. This realization automatically triggers your body’s self-defense mechanism as it tries to help protect you. Within a few seconds some typical reactions occur: Adrenaline is released to improve your alertness, additional blood is sent to your muscles in case you need to defend yourself physically, your skin glands become more active in preparation for a physical response, your digestive process slows down, and your breathing changes. After this reaction takes place, you are better prepared to deal with the crisis you are faced with and can make a conscious decision about what to do.

What is more important than the lie itself is the reason for telling the lie. When we do something wrong, such as commit a crime or do something we know we shouldn’t have done, we realize that if we get caught that we will be punished. This punishment might be imprisonment, embarrassment, loss of a present or future job, loss of money, or loss of a relationship. Our instinct for self-preservation makes us want to avoid being punished for what we did. This is usually accomplished by lying.

In other words, lying in most cases is an act of self-defense. We usually lie to avoid punishment. Being caught in the lie means we will be punished. It is our understanding of the consequences that triggers the body’s self-defense mechanism when we lie. The polygraph instrument is a finely tuned diagnostic device which will record various aspects of your body’s Sympathetic and Parasympathetic Nervous Systems and will recognize when your body’s self-defense mechanism has been activated by lying. It isn’t the lie that makes a polygraph work, it’s the understanding that there are consequences to being caught in that lie. Our bodies create self-defense reactions to try to avoid those consequences.

Another operative element in polygraph testing is known as “cognitive dissonance.” People normally tell the truth. It requires no effort. When we lie, we must force ourselves to do so in conflict with what our bodies would normally do. This conflict within us creates a reaction because we have to consciously “fight” our body’s normal (truthful) responses, and the resulting reaction causes some of the changes seen with a polygraph instrument in deceptive people.
1. All polygraph questions must be formulated to elicit a “Yes” or “No” answer.

2. All polygraph questions must be objective and unambiguous. This means that every person who hears the question must give it the same interpretation.

3. Each polygraph question must be short.

4. Polygraph questions must not be hypothetical.

5. Polygraph questions must not ask about opinions, emotions, feelings, or the future.

6. Polygraph questions should avoid being compound (multi-part).

7. Polygraph questions should be as direct as possible. E.g. “Did you kill John Doe” and not “Are you telling the truth about the death of John Doe”

8. A separate exam should be used for each issue. E.g., Questions about “being an alcoholic” should not be asked in the same polygraph exam with questions about “taking bribes.”
The polygraph instrument records the body’s Sympathetic Nervous System which is part of the Autonomic Nervous System. The Autonomic Nervous System operates independently of our conscious thought and will produce activity regardless of whether or not we want it to. E.g., the lungs and heart will continue to operate even when someone is asleep, regardless of whether or not the person is thinking about it. Attempts to change or manipulate these systems are usually picked up by the polygraph examiners. It is, therefore, highly unlikely that someone can alter the outcome of a polygraph exam. This is why polygraph has a verified accuracy rate that is significantly higher than 90%. In contract, eyewitness identification has an accuracy rate of about 73%.

Most polygraph examiners are now using “countermeasures detection” instrument which easily identifies anyone attempting to manipulate or change the polygraph results. Unfortunately, many honest people are found “deceptive” to the test questions when they attempt to influence their test results. When an examiner discovers that the examinee is doing things to affect the charts, the result is either “deception indicated” or “inconclusive.” In other words, a person will not pass a polygraph by using these techniques. In fact, recent research (2008-2009) has determined that in most cases when someone attempts to “beat” a polygraph, their test results actually get worse. Use of certain drugs and medications can also affect the exam, but such use generally results in an “inconclusive” test. It is virtually impossible to change a result from “deceptive” to “truthful” through the use of drugs or medications prior to an exam. If drugs are suspected, a pre-test (or post-test) drug screening is advised.
No Examiner should inquire into any of the following areas during Pre-employment or Periodic Employment Polygraph Examinations:

Religious beliefs or affiliations (unless specifically relevant to the job)
Beliefs or opinions regarding racial matters (except to the extent that any such biases could interfere with one’s ability to fairly and objectively perform his or her job)
Political beliefs or affiliations
Beliefs, affiliations or lawful activities regarding unions or labor organizations
Lawful sexual preferences or activities
Polygraph results should be released only to authorized persons. Generally, those the persons who should receive the results are the examinee and anyone specifically designated in writing by the examinee such as the person, firm, corporation or governmental agency that requested the examination, and others as may be required by law.

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