What Is A Polygraph?
Lie detector tests have become a very popular cultural icon thanks to crime dramas and comedies. The idea that a person's credibility can be detected by monitoring psychophysiological changes is more of a myth than reality. Even the term "lie detector," that used to refer to polygraph testing is a misnomer. Click here
The instrument typically used to conduct polygraph tests consists of a recorder that assesses three indicators of autonomic activation: heart rate and blood pressure, respiration, and skin conductivity. Most examiners today utilise computerised recording systems where the rate and depth of respiration are measured by pneumographs wrapped around a subject's chest while a blood pressure cuff assesses cardiovascular activity. Skin conductivity is measured through electrodes attached to a subject's fingertips.
A typical examination also includes a pretest phase during which a pretest interview is designed to ensure that subjects understand the questions and induce a subject's concern about lying. Polygraph examinations usually include a procedure called a "stimulation test," which is a demonstration of the instrument's accuracy.
Several questioning techniques are commonly employed in polygraph tests and the most widely used test format compares responses to "relevant" questions with those of "control" questions. The control questions are designed to control the effect of the threatening nature of relevant issues.
The validity of polygraph testing has been a controversial topic for a long time. The major problem is that there is no evidence that any pattern of physiological reactions is unique to deception. In real-world situations, it's tough to know the exact nature of the truth.
Another problem is that polygraph research has not separated effects like the subject's belief in the effectiveness of the. One reason that polygraph tests may appear accurate is that people who believe that this test works and that they can be caught may confess their guilt or will be very anxious and nervous when questioned. If this idea is correct, the lie detector is better off called a fear detector.
Some confusion about polygraph test accuracy arises because they are used for different purposes, and for each context different theory and research is applicable. Also, there is evidence that indicates that strategies used to "beat" polygraph examinations may be effective. Countermeasures include simple physical movements and psychological interventions.
Despite the lack of good research for the validation of polygraph tests, efforts are still on-going to develop and assess new approaches. Some work involves the use of additional autonomic indicators, such as cardiac output and skin temperature. These are however more specific to deception than polygraph tests.
Significance & Practical Application
The development of currently used "lie detection" techniques has been based on ideas about physiological functioning but has mostly been independent of systematic psychological research.
Early theorists believed that deception required effort and, thus, could be assessed by monitoring physiological changes but these have not been proven and basic research remains limited on its nature. Efforts to develop actual tests have always outpaced theory-based basic study, but without a better understanding of the way deception functions, development of a lie detection technology seems highly improbable.
But for now, though the idea of a lie detector may sound cool, it is better to remain sceptical about any conclusion is drawn from a polygraph.
