should not be counted on for detection: they will not detect more than a small proportion of major security violators who do not admit their actions.

We have thought hard about how to advise government agencies on whether or how to use information from a diagnostic screening test that has these serious limitations. We note that in medicine, such imperfect diagnostics are often used for screening, though only occasionally in populations with very low base rates of the target condition. When this is done, either the test is far more accurate than polygraph testing appears to be, or there is a more accurate (though generally more invasive or expensive) follow-up test that can be used when the screening test gives a positive result. Such a follow-up test does not exist for the polygraph. The medical analogy and this difference between medical and security screening underline the wisdom in contexts like that of employee security screening in the DOE laboratories of using positive polygraph screening results—if polygraph screening is to be used at all—only as triggers for detailed follow-up investigation, not as a basis for personnel action. It also underlines the need to pay close attention to the implications of false negative test results, especially if tests are used that yield a low proportion of positive results.

A belief that polygraph testing is highly accurate probably enhances its utility for such objectives as deterrence. However, overconfidence in the polygraph—a belief in its accuracy that goes beyond what is justified by the evidence—also presents a danger to national security objectives. Overconfidence in polygraph screening can create a false sense of security among policy makers, employees in sensitive positions, and the general public that may in turn lead to inappropriate relaxation of other methods of ensuring security, such as periodic security re-investigation and vigilance about potential security violations in facilities that use the polygraph for employee security screening. It can waste public resources by devoting to the polygraph funds and energy that would be better spent on alternative procedures. It can lead to unnecessary loss of competent or highly skilled individuals in security organizations because of suspicions cast on them by false positive polygraph exams or because of their fear of such prospects. And it can lead to credible claims that agencies that use polygraphs are infringing civil liberties for insufficient benefits to the national security. Thus, policy makers should consider each application of polygraph testing in the larger context of its various costs and benefits.


CONCLUSION: Some potential alternatives to the polygraph show promise, but none has yet been shown to outperform the poly-

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