The Accuracy of Human Decisions and Objective Measurements in Psychophysiological Detection of Knowledge

I examined the relative detection efficiency of three measurements—skin resistance response (SRR) amplitude, respiration line length (RLL), and human respiration response evaluation (RRE)—in a guilty knowledge experiment. Thirty-two subjects were presented with lists of personal information in which only one of five items was correct. Subjects were instructed to try to avoid detection of the relevant items in the polygraph test. All three measurements discriminated better than chance between relevant and neutral items, with the objectively measured SRR and RLL superior to the subjective RRE. When SRR and RLL were compared for their relative efficiency, the former yielded better detection. The differentiation was even better with a measure that combined the SRR and the RLL. The results are discussed with respect to previous findings and practical implications.