sults to the field context is an issue of “external validity” of the laboratory studies, that is, of the extent to which the study design, combined with any external knowledge that can be brought to bear, support the relevance of the findings to circumstances other than those of the laboratory study. For example, an externally valid polygraph study would suggest that the accuracy observed in it would also be expected for different types of examinees, e.g., criminals or spies instead of psychology students or respondents to newspaper advertising; interviews of different format or subject matter, e.g., comparison question tests for espionage screening instead of for investigations of a mock theft; examiners with differing backgrounds, e.g., police interrogators rather than full-time federally trained examiners; and in field situations as well as in the laboratory context.

If, as we believe, the polygraph is closely analogous to a clinical diagnostic test, then both psychophysiological theories of polygraph testing and experiences with other clinical diagnostic tests offer useful insights regarding the external validity of laboratory polygraph accuracy for field contexts. Each perspective raises serious concerns about the external validity of results from laboratory testing in the field context.

Higher Stakes. The theory of question construction in the comparison question polygraph technique relies at its core on the hypothesis that emotional or arousal responses under polygraph questioning increase the more concerned examinees are about being deceptive. Thus, innocent examinees are expected to show stronger responses to comparison than to relevant questions. This hypothesis suggests that factors that increase this concern, such as the costs of being judged deceptive, would increase emotional or arousal response and amplify the differences seen between physiological responses to relevant and comparison questions. On the basis of this hypothesis, one might expect polygraph accuracy in laboratory models to be on average somewhat below true accuracy in field practice, where the stakes are higher. There is a plausible contrary hypothesis, however, in which examinees who fear being falsely accused have strong emotional responses that mimic those of the truly deceptive. Under this hypothesis, field conditions might have more false-positive errors than are observed in the laboratory and less accuracy.

Under orienting theory, which provides the rationale for concealed information polygraph testing, it is the recognition of a novel or significant stimulus that is presumed to cause the autonomic response. Increasing the stakes might increase the significance of the relevant item and thus the strength of the orienting response for examinees who have concealed information, with the result that the test will do better at detecting such information as the stakes increase. However, as with arousal-based

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