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Abstract

KIRCHER, J. C., PACKARD, T.; BELL, B. G.; and BERNHARDT, P. C. (1997) Comparison of Skin Conductance and Skin Resistance Measures for the Detection of Deception October 2001, Report No. DoDPI02-R-0001. Department of Defense Polygraph Institute, Fort Jackson, SC 29207-5000.

Traditional analog polygraph instruments typically record skin resistance (SR), whereas academic psychophysiologists typically record skin conductance (SC) and have argued that SC is superior to SR. The present study tested if SC or SR is more useful for the detection of deception. 336 participants in a previous experiment (DODPI97-P-0016) were tested about their participation in a mock theft. Half of the participants were guilty of committing the theft, and the other half were innocent. Probable-lie polygraph tests (PL) were administered to half of the innocent and half of the guilty participants, and directed-lie tests (DL) were administered to the remaining participants. Participants were paid $30 and were offered an additional $50 to convince the polygraph examiner of their innocence. Digitized recordings of SC subsequently were transformed to SR. A computer measured the amplitudes and other features of SC responses and SR responses to comparison and relevant test questions. Both SC and SR were highly diagnostic of truthfulness and deception, and no evidence was found to favor either SC or SR for either PL or DL polygraph tests. Univariate analyses revealed no differences between SC and SR in their ability to discriminate between truthful and deceptive individuals, and multivariate analysis indicated that either measure might be used in combination with other physiological measures to detect deception. However, these conclusions apply only to SR recordings obtained when a constant-voltage is applied to wet electrodes. Additional research would be needed to compare such laboratory-grade measurements of SC and SR to electrodermal activity as it is measured by traditional analog and newer computerized field polygraphs.