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The Polygraph and Lie Detection
cent correct depends on the threshold used for making a judgment of deceptiveness and on the base rate of examinees who are being deceptive.
The large majority of the studies we reviewed involve specific-issue examinations, in which relevant questions are tightly focused on specific acts. Such studies have little direct relevance for the usual employee screening situation, for three reasons. First, in screening, the test is not focused on a single specific act, so the examiner can only ask questions that are general in nature (e.g., have you had any unauthorized foreign contacts?). These relevant questions are arguably more similar to comparison questions, which also ask about generic past actions, than is the case in specific-incident testing. It is plausible that it will be harder to discriminate lying from truth-telling when the relevant and comparison questions are similar in this respect.
Second, because general questions can refer to a very wide range of behaviors, some of which are not the main targets of interest to the agencies involved (e.g., failure to use a secure screen saver on a classified computer while leaving your office to go to the bathroom), the examinee may be uncertain about his or her own “guilt.” Examinees may need to make a series of complex decisions before arriving at a conclusion about what answer would be truthful before deciding whether to tell the truth (so defined) or fail to disclose this truthful answer. Instructions given by examiners may alleviate this problem somewhat, but they are not likely to do so completely unless the examinee reveals the relevant concerns.
Third, the base rate of guilt is usually very low in screening situations, in contrast with specific-incident studies, in which the percentage of examinees who are guilty is often around 50 percent and almost always above 20 percent. Examiners’ expectations and the examiner-examinee interaction may both be quite different when the base rates are so different. In addition, the implications of judging an examinee deceptive or truthful are quite different depending on the base rate, as we discuss in detail in Chapter 7.
A small number of studies we reviewed did specifically attempt to estimate the accuracy of the polygraph for screening purposes. Given the centrality of screening to our charge, we offer detailed comments on the four studies that met our minimal quality standards as well as three others that did not. Four of these seven studies (Barland, Honts, and Barger, 1989; U.S. Department of Defense Polygraph Institute, 1995a, 1995b; Reed, no date) featured general questions used in examinations of subjects, some of whom had committed specific programmed transgressions. While this “mock screening situation,” as it was termed by Reed (no date), is an