Ingram, E. M. Effects of electrodermal lability and anxiety on the detection of deception with the control question technique. September 1994, Report No. DoDPI94-R-0004. Department of Defense Polygraph Institute, Ft. McClellan, AL 36205.
This exploratory study was designed to examine the effects of individual differences in electrodermal lability or spontaneous electrodermal responding, and state-trait anxiety on the detection of deception using the skin conductance response (SCR). Eighty-two males participated in this study. Half were assigned to the programmed innocent group and half were assigned to the programmed guilty group. Data were analyzed from the 75 subjects who completed the study. At the beginning of the study each subject completed the Self-Evaluation Questionnaire, forms Y1 and Y2 of the State-Trait Anxiety Inventory (STAI). The STAI measures situational (state) and inherent (trait) anxiety. Upon completion of the inventory, subjects individually underwent a session in which nonspecific, spontaneous SCR were recorded for 5 minutes. This was followed by the repeated presentation of a 70 dB, 1000 Hz tone of 5-second duration until habituation occurred. Habituation criterion was two consecutive nonresponse trials. Immediately following the habituation trials a Control Question Test, Psychophysiological Detection of Deception examination was conducted. The tests were scored by two examiners, blind to the group assignment of the subjects. Data analyses indicated that the proportion of the subject sample accurately detected using SCR amplitudes was not significantly above chance. The detection level of the blind scorers, who used traditional scoring methods was not significantly above chance, however, the interrater reliability (measured by a multiple rater kappa test) was significantly above chance. No significant relationships were found among electrodermal lability and state or trait anxiety and the detection of deception.
Keywords: electrodermal lability, skin conductance response, individual differences, control question test, detection of deception, state-trait anxiety, habituation rate
Among the many variables suspected of influencing the results of a psychophysiological detection of deception (PDD) examination is a category which psychologists label individual differences. Individual differences include all of the features and characteristics which make one individual different from another. These include physical characteristics such as height, weight, hair color, limb length, and psychological characteristics such as introversion, intelligence, general anxiety level, and aggressiveness. In most PDD research studies it is assumed, though obviously not correctly, that all examinees are essentially the same. Failure to correctly determine subject veracity is generally attributed to inappropriate or incorrect procedures, lack of instrument sensitivity, or examiner errors. In many cases, however, the problem could be due to the failure or inability to properly assess and respond to individual differences among examinees. Perhaps the accuracy of a PDD examination can be improved if individual differences are properly evaluated and accommodated.
This report describes an exploratory attempt to measure individual differences in anxiety and to evaluate how those differences influence skin conductance responses. This is a preliminary attempt to address an important area of concern to the PDD discipline.