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The Polygraph and Lie Detection
As its name implies, the relevant-irrelevant test format compares examinee responses to relevant and irrelevant questions. A relevant question is one that deals with the real issue of concern to the investigation. These questions include asking whether the examinee perpetrated the target act or knows who did it and perhaps questions about particular pieces of evidence that would incriminate the guilty person. An irrelevant question is one designed to provoke no emotion (e.g., “Is today Friday?). Irrelevant questions are typically placed in the first position of a question list because the physiological responses that follow the presentation of the first question are presumed to have no diagnostic value; they are also placed at other points in the question sequence. Guilty examinees are expected to show stronger reactions to relevant than to irrelevant questions; innocent examinees are expected to react similarly to both question types.
The relevant-irrelevant test format was the first widely used polygraph testing format and was long the dominant format. The format was originally used in criminal testing. Currently, it is also used in multiple-issue screening applications, for example, at the U.S. National Security Agency.
Relevant-irrelevant polygraph tests are not normally standardized for question selection or for interpretation. Examiners typically interpret the test results globally by inspecting the charts to see whether or not there is a pattern of stronger responses to relevant questions. The lack of standard procedures for administration and scoring makes the relevant-irrelevant test unsuitable for scientific evaluation. It is not possible to support general conclusions about its accuracy because the procedure can vary uncontrollably across examiners and examinations. Polygraph researchers generally consider the test outmoded. For example, Raskin and Honts (2002:5) conclude that the relevant-irrelevant test “does not satisfy the basic requirements of a psychophysiological test and should not be used.”
COMPARISON QUESTION (CONTROL QUESTION) TEST
Comparison question tests (also called control question tests) compare examinees’ responses to relevant questions to their responses to other questions that are believed to elicit physiological reactions from innocent examinees. Relevant questions are defined as in the relevant-irrelevant test. Comparison questions ask about general undesirable acts, sometimes of the type of an event under investigation. For example, in a burglary investigation, one comparison question might be “Have you