• Detection of deception;
  • Electrodermal differentiation;
  • Guilty knowledge paradigm;
  • Intention to deceive;
  • Motivation to avoid detection


The present study focused on electrodermal differentiation between relevant and neutral items in the Guilty Knowledge paradigm. Three factors were varied in a between-subjects design. The role of deception was examined by varying the type of verbal answer to the questions (“yes,”“no,” and remaining silent). The intention to deceive factor was examined by contrasting subjects told to delay their answer (“yes” or “no”) with those told to produce their answer immediately. Finally, motivation to avoid detection was manipulated by having half the subjects monetarily rewarded for an important (ego relevant) detection task (high motivation), whereas the remaining subjects were neither rewarded nor told that the task was important. The results indicated that a deceptive answer (“no”) to the relevant question was associated with an increased differential skin conductance responsivity, but better than chance detection rates were obtained with truthful (“yes”) and silent conditions. Equal and significant detection rates were observed when the responses were computed immediately following question presentation, whether the subjects had answered immediately or had delayed their answers. In contrast, differential electrodermal responsivity to the delayed answers was markedly attenuated. The motivation factor had no main or interactive effects on differential responsivity. The present results, together with those obtained in previous studies, suggest that whereas deception is neither a necessary nor a sufficient condition for psychophysiological detection, it may facilitate detection. Possible mechanisms through which such a facilitation could occur were considered.