NCJ Number
100428
Date Published
1986
Length
132 pages
Annotation
The effects of motivation (as a between-subjects factor) and the reality of information on the guilty-knowledge technique (GKT) in suspect interrogation were investigated in two experiments.
Abstract
The GKT is a psychophysiological method of detecting concealed information by monitoring a suspect's skin conductance while he answers multiple-choice questions containing critical and noncritical items. In the first experiment, 119 males were assigned to 1 of 6 groups in a 3 (motivation to conceal information) by 2 (realtiy) factorial design. The reality levels were real and not real; the motivation levels were high, low, and control. Detection rates, number of electrodermal responses, and skin conductance were scored. The high motivation group had more responses and was detected more often than the low and control motivation groups. There were no significant differences between the reality groups. In the second experiment involving 40 subjects, only high and low motivation conditions were used and reality level was a within-subjects factor. Larger skin conductance amplitudes were found for real than for not-real information. There were no differences between the motivation conditions. Taken together, results indicate that the reality value of stimulus materials is strongly influenced by the instructions given to the subject and the incentives for performance. Tabular data, supplementary research materials, and 34 references. (Author abstract modified)