teristics of examinees, and in the nature and context of investigations than arises in typical field applications. Observational studies of polygraph testing in the field are plagued by selection and measurement biases, such as the inclusion of tests carried out by examiners with knowledge of the evidence and of cases whose outcomes are affected by the examination. In addition, they frequently lack a clear and independent determination of truth. Due to these inherent biases, observational field studies are also highly likely to overestimate real-world polygraph accuracy.

CONCLUSION: Notwithstanding the limitations of the quality of the empirical research and the limited ability to generalize to real-world settings, we conclude that in populations of examinees such as those represented in the polygraph research literature, untrained in countermeasures, specific-incident polygraph tests can discriminate lying from truth telling at rates well above chance, though well below perfection. Because the studies of acceptable quality all focus on specific incidents, generalization from them to uses for screening is not justified. Because actual screening applications involve considerably more ambiguity for the examinee and in determining truth than arises in specific-incident studies, polygraph accuracy for screening purposes is almost certainly lower than what can be achieved by specific-incident polygraph tests in the field.

The accuracy levels in the four screening simulations in our sample, which include a validation study of the Test for Espionage and Sabotage (TES) used in the employee security screening program of the U.S. Department of Energy (DOE), are in the range reported for other specific-incident laboratory studies. The one field study of actual screening presents results consistent with the expectation that polygraph accuracy in true screening situations is lower.

Countermeasures

Countermeasures pose a potentially serious threat to the performance of polygraph testing because all the physiological indicators measured by the polygraph can be altered by conscious efforts through cognitive or physical means. Certain countermeasures apparently can, under some laboratory conditions, enable a deceptive individual to appear nondeceptive and avoid detection by an examiner. It is unknown whether a deceptive individual can produce responses that mimic the physiological responses of a nondeceptive individual well enough to fool an examiner trained to look for behavioral and physiological signatures of countermeasures. The available research provides no information on whether innocent examinees can increase their chances of achieving nondeceptive



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