LIE DETECTORS

Polygraphs, or instruments used to discover whether a person is lying, are commonly called lie detectors. Polygraphs are utilized in courts, in the government, and in private businesses. However, they are controversial. Many people don't believe that polygraphs can accurately identify whether an individual is lying, while others believe that polygraphs are simply tools to intimidate¹ people into confessing guilt, regardless of whether they're really lying.

The older, analog polygraph machine consists of three styluses-or pens-and a roll of paper that slides across the machine. The styluses, which draw lines on the paper and record changes in the subject's condition, are connected to wires, which are in turn connected to the test subject. A mostly straight line indicates there is minimal variation in the subject's body. A jagged² line with multiple peaks and valleys illustrates a large amount of variation. Modern digital polygraphs are interpreted in a fashion identical³ to analog polygraphs; however, instead of paper, the lines are displayed on a computer monitor.

Polygraph tests are interviews. Examiners ask subjects questions, and when subjects answer, their body reactions are recorded by the polygraph. During the interviews, examiners document the behavior of the lines on the paper subsequent to each question. Later, examiners use these results to assess the likelihood that the subject is telling the truth. When lying, individuals are often apprehensive⁴ about being caught, and this uneasiness produces stress. Stress triggers elevated heart and breathing rates and an increase in perspiration⁵, all of which are then detected by the polygraph.

To detect changes in respiration, rubber tubes filled with air are positioned around subjects' torsos, and as subjects breathe, the air in the tubes is compressed⁶, and the tubes expand. When the tubes expand, they push against a part of the polygraph called the bellows. The greater the expansion of the tubes, the greater the contraction of the bellows, which moves an arm on the polygraph. Breathing quickly results in an irregular line on the test. To measure heart rate, subjects wear bands around their wrists⁷. A tube connects the band to a second arm on the polygraph. As blood travels through the wrist, it creates very small sounds, and when subjects experience stress, the sounds become louder and faster. These sounds move the air in the tube, and the air pushes the bellows, moving the arm on the polygraph. A stronger, faster heart rate results in a more jagged line. Finally, the polygraph measures perspiration on the fingertips with metal plates called galvanometers, which are attached to two fingers. The galvanometers measure the skin's conduction of electricity. When people perspire, the skin becomes wet, and if subjects' skin is wetter than usual, it conducts more electricity. The galvanometers are connected to the third arm of the polygraph, and if the skin starts to increase in electrical conduction, movement of the arm increases. A comparison of the movements of all three arms should reveal to the examiner increases in stress for certain questions.

Many people debate the reliability of polygraphs. They believe that although these tests measure variations in the body associated with stress, these variations could be the result of other kinds of emotions. While some people experience minimal to no stress when lying, some honest people may experience intense stress from the exam itself. Because of this, it is possible for the examiner to wrongly deduce⁸ that the subject is lying, and the subject might then be unfairly punished. Even companies that produce polygraphs indicate that the mechanisms cannot detect lies, suggesting that polygraphs can only identify behavior that should not be trusted. Because of these criticisms, polygraph data cannot be used as evidence in American courts. Also, American law prohibits private companies from forcing employees to take polygraph tests. Despite this, both the American government and businesses continue to utilize polygraphs. In fact, workers for government agencies can be fired if they fail or refuse to take a polygraph test. Various opponents of polygraphs have concluded from this fact that the tests are used to intimidate workers, to make them confess to wrongdoing, or prevent them from complaining about company policies. Regardless, it's clear that polygraph tests will continue to affect the lives of employees.

• heart rate, etc.
• limited legally
• falsely identify
• reactions to stress
• detect deception
• examiners interview

• accurately
• conduction
• minimal
• punish
• reliability
• likelihood

The Polygraph Test

A common polygraph test has several parts. The first part is an interview between the examiner and the subject, during which the two learn about each other. This is intended to reduce the subject's stress levels while allowing the examiner to see how the subject answers neutral questions.

After the interview, the examiner prepares the set of questions that he or she will ask during the polygraph test. Before the test, the examiner informs the subject what the questions will be; this reduces unnecessary stress that could make the results of the test more difficult to evaluate.

Next comes the actual test, during which the examiner asks about ten questions. Some of these questions are neutral, such as "Is your name (insert name)?" Others are control questions, which are designed to receive an untruthful answer but are not related to the offense being investigated. An example might be, "Have you ever stolen anything in your life?" The subject's response to these mildly stressful questions can then be compared to his or her response to the relevant questions.

After all the questions have been asked, the examiner checks the data from the polygraph. If the subject's stress level remained mostly the same throughout the test, the examiner may conclude the subject was honest. However, if there were moments when the subject's stress increased sharply, especially if this happened when he or she answered a specific question, then the examiner may conclude otherwise.