positive response as a possible indication of deception to any question, not necessarily the specific one for which deception was indicated.

We have also examined preliminary and as yet unfinished reports on two subsequent DoDPI “screening” studies, carried out in 1997 and in 2001. These studies share many characteristics of the earlier DoDPI research, and their results do little to assuage our concerns regarding the limited scientific support for the validity of the Test for Espionage and Sabotage (TES) as a screening instrument.

This section summarizes the evidence on accuracy related to particular issues. Because the quantitative data are so sparse for many important issues, each section also includes qualitative judgments about the likely meaning of what we know for polygraph interpretation (e.g., judgments about the robustness of polygraph evidence across examinee populations).

Individual differences in psychophysiological measures are common. Such differences have been reported in measures of many response systems, including the electrodermal, cardiovascular, endocrine, and central nervous systems. A growing body of research indicates that such differences in adults are moderately stable over time and are associated with a wide range of theoretically meaningful behavioral measures (see Kosslyn et al., 2002, for a review).

One of the earliest reported individual differences in a psychophysiological measure that was meaningfully associated with behavior is in electrodermal lability (Crider and Lunn, 1971). This is defined as the frequency of “nonspecific” electrodermal responses—responses that are observed in the absence of any external eliciting stimulus. A few studies have investigated whether this individual difference variable affects the accuracy of the polygraph, with inconsistent results. In two studies, Waid and Orne (1980) found that electrodermally stabile subjects (those exhibiting relatively few spontaneous responses) were less frequently detected in a concealed information task in comparison with electrodermally labile subjects. The number of items detected on the concealed information test was positively correlated with the frequency of nonspecific electrodermal responses. In addition, among innocent subjects, those with higher levels of electrodermal lability were more frequently falsely identified as deceptive. These studies only analyzed electrodermal activity; consequently, is not clear how much the accuracy of a full polygraph would have been