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The Polygraph and Lie Detection
accused are themselves vital to national security. For this reason, tradeoff decisions are best made by elected officials or their designees, aided by the principles and practices of behavioral decision making.
We first summarize what scientific analysis can contribute to understanding the tradeoffs involved in using polygraph tests in security screening. (These tests almost always use the comparison question or relevant-irrelevant formats because concealed information tests can only be used when there are specific pieces of information that can form the basis for relevant questions.) We then discuss possible strategies for making the tradeoffs more attractive by improving the accuracy of lie detection— either by making polygraph tests more accurate or by combining them with other sources of information. We also briefly consider the legal context of policy choices about the use of polygraph tests in security screening.
TRADEOFFS IN INTERPRETATION
The primary purpose of the polygraph test in security screening is to identify individuals who present serious threats to national security. To put this in the language of diagnostic testing, the goal is to reduce to a minimum the number of false negative cases (serious security risks who pass the diagnostic screen). False positive results are also a major concern: to innocent individuals who may lose the opportunity for gainful employment in their chosen professions and the chance to help their country and to the nation, in the loss of valuable employees who have much to contribute to improved national security, or in lowered productivity of national security organizations. The prospect of false positive results can also have this effect if employees resign or prospective employees do not seek employment because of polygraph screening.
As Chapter 2 shows, polygraph tests, like any imperfect diagnostic tests, yield both false positive and false negative results. The individuals judged positive (deceptive) always include both true positives and false positives, who are not distinguishable from each other by the test alone. Any test protocol that produces a large number of false positives for each true positive, an outcome that is highly likely for polygraph testing in employee security screening contexts, creates problems that must be addressed. Decision makers who use such a test protocol might have to decide to stall or sacrifice the careers of a large number of loyal and valuable employees (and their contributions to national security) in an effort to increase the chance of catching a potential security threat, or to apply expensive and time-consuming investigative resources to the task of identifying the few true threats from among a large pool of individuals who had positive results on the screening test.