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Abstract

HONTS, C. R. and CARLTON, B. L. The effects of incentives on the detection of deception. May 1990, Report No. DoDPI90-R-0003. Department of Defense Polygraph Institute, Ft. McClellan, AL 36205.

A mock crime experiment was conducted to explore the effects of manipulating motivation to deceive on the physiological detection of deception using the control question test. Sixty subjects were assigned to one of four conditions in a 2 X 2 factorial design (two motivational states crossed with innocence or guilt). The motivation manipulation failed to produce any significant effects. The control question test performed reasonably well. The original examiners' outcomes with guilty subjects were 80% correct, 7% incorrect and 13% were inconclusive. With the innocent subjects the original examiners' outcomes were 50% correct, 17% incorrect and 33% were inconclusive. Electrodermal measures provided the greatest discriminability between innocent and guilty subjects followed by respiratory and cardiovascular measures. The results add to the already complex set of motivation results in the literature, and they were discussed within the context of Steller's systems theory, previous research, and research needed in the future.

Key-words: detection of deception, motivation, control question test

Director's Foreword

This report describes a study designed to determine if psychophysiological detection of deception (PDD) accuracy is affected by offering examinees an incentive to be found non- deceptive. This is one of several published studies designed to address the influence of motivation on PDD examination decision accuracy. The authors interpret the analysis results as indicating that the incentive used in the study did not influence PDD examination decision accuracy. Results of some other studies support this conclusion while those of others do not. The authors are careful to suggest that the incentive used may not have been of sufficient strength to influence responding. Additional analyses are provided regarding the accuracy of PDD examination decisions made by the original examiner, a blind examiner, and an automated scoring system.

While the results of this study suggest that examinee motivation does not effect the accuracy of PDD examination decisions, this conclusion should be interpreted with caution. The relationship between incentives, motivation, and behavior has not been precisely defined, nor is it clearly understood. In addition, the relatively small number of observations per group (15) could have provided insufficient data to adequately test the hypothesis. The question posed is, however, of great interest and importance to the forensic psychophysiology discipline and should be further investigated.

Michael H. Capps

Director