Electrodermal differentiation of deception: perceived accuracy and perceived memorial content manipulations

The demonstration of deception as a psychophysiological phenomenon requires a comparison of physiological responses to two conditions (experimental and control) which differ only with respect to deception. Such electrodermal (skin conductance response) differentiation was recently reported in the Differentiation of Deception paradigm, which controls for two potentially important sources of confounding in polygraph (often referred to as the Detection of Deception): differential question significance and differential frequency of question occurrence. The present study manipulated (between 32 subjects in a 2 x 2 design) two two-level, subjective factors in the paradigm: Perceived Accuracy of polygraphy (written and oral instructions characterising accuracy as high vs low) and Perceived Memorial Content (20 more complex, less personal, and less meaningful questions vs 6 less complex, more personal, and more meaningful questions). Significant differentiation of deception was again obtained, as was evidence for the effectiveness of the manipulations. However, the deception phenomenon was not clearly affected by either of the two subjective factors. In addition, one post-hoc test showed significantly increased differentiation under the low Perceived Accuracy condition, which is contrary to the widespread belief of polygraphers that high perceived accuracy is not only important but even essential for the detection of deception. However, the applied, polygraphic aim of detecting guilt in individuals is quite different from the scientific, psychophysiological aim of differentiating deception as a psychological process, and the phenomena involved probably have different causes.