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The Polygraph and Lie Detection
Third, these estimates are based only on examinations of certain populations of polygraph-naïve examinees untrained in countermeasures and so may not apply to other populations of examinees, across testing situations, or to serious security violators who are highly motivated to “beat” the test. Fourth, even for naïve populations, the accuracy index most likely overestimates performance in realistic field situations due to technical biases in field research designs, the increased variability created by the lack of control of test administration and interpretation in the field, the artificiality of laboratory settings, and possible publication bias.
Thus, the range of accuracy indexes, from 0.81 to 0.91, that covers the bulk of polygraph research studies, is in our judgment an overestimate of likely accuracy in field application, even when highly trained examiners and reasonably well standardized testing procedures are used. It is impossible, however, to quantify how much of an overestimate these numbers represent because of limitations in the data. In our judgment, however, reliance on polygraph testing to perform in practical applications at a level at or above A = 0.90 is not warranted on the basis of either scientific theory or empirical data. Many committee members would place this upper bound considerably lower.
Despite these caveats, the empirical data clearly indicate that for several populations of naïve examinees not trained in countermeasures, polygraph tests for event-specific investigation detect deception at rates well above those expected from random guessing. Test performance is far below perfection and highly variable across situations. The studies report accuracy levels comparable to various diagnostic tests used in medicine. We note, however, that the performance of medical diagnostic tests in widespread field applications generally degrades relative to their performance in validation studies, and this result can also be expected for polygraph testing. Existing polygraph field studies have used research designs highly vulnerable to biases, most of which exaggerate polygraph accuracy. We also note that the advisability of using medical diagnostic tests in specific applications depends on issues beyond accuracy, particularly including the base rate of the condition being diagnosed in the population being tested and the availability of follow-up diagnostic tests; these issues also pertain to the use of the polygraph.
The great bulk of validation research on the polygraph has investigated deception associated with crimes or other specific events. We have found only one true screening study; the few other studies that are described as screening studies are in fact studies focused on specific incidents that use relatively broad “relevant” questions. No study to date