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The Polygraph and Lie Detection
measure cardiac sympathetic activation (e.g., Berntson et al., 1994; Cacioppo et al., 1994).
Because some of these measures are closer than polygraph-based measures to the specific physiological processes associated with arousal, there are theoretical reasons to expect that they might offer better indicators of arousal than those used in polygraph testing. However, although some of these measures have advantages over polygraph measures on grounds of theoretical psychophysiology, they may not actually map more closely to psychological variables. Like the polygraph indicators, measures such as myocardial contractility and respiratory sinus arrhythmia are influenced by sundry social and psychological factors (e.g., Berntson et al., 1997; Gardner, Gabriel, and Diekman, 2000). These factors might result in false positive test results if an examinee is aroused by something other than deception (e.g., a concern about false accusations) or might provide a basis for countermeasures.
Despite these caveats, various researchers have proposed the use of some of these autonomic measurements as alternatives or adjuncts to the four basic channels that are part of the standard polygraph measurement instrument. The limited research on these measures does not offer any basis for determining where they may fit in the array of possible physiological measurements. The studies generally report on the accuracy of tests using a particular measure in small samples or in uncontrolled settings.
A recent report on thermal imaging illustrates the difficulties we have had in assessing whether these peripheral measures are promising and precisely how research on them should be pursued. In 2001, investigators at the U.S. Department of Defense Polygraph Institute (DoDPI), collaborating with outside researchers, carried out a pilot study (Pollina and Ryan, 2002) using a comparison question format polygraph for a mock crime scenario with 30 examinees who were trainees at an army base. Their goal was to investigate the possible utility of a new device for thermography that measures the radiant energy emitted from examinees’ faces, as an adjunct or alternative to the traditional polygraph measurements. Thermography has an important potential advantage over the polygraph in that it does not require an examinee to be hooked up to a machine.
Five of the original examinees in the study were dropped because they were uncooperative or had other problematic behavior. Of the remaining 25, 12 were programmed to be deceptive and 13 were programmed to be nondeceptive. The outside researchers published a report (Pavlidis, Eberhardt, and Levine, 2002) claiming that the thermal imaging results alone achieved higher accuracy than the polygraph on nondeceptive examinees (11 of 12 subjects correct for thermal imaging compared