Electrodermal differentiation of deception: the effect of choice versus no choice of deceptive items

In the differentiation-of-deception paradigm (DDP), the experimental and control conditions, respectively, consist of questions answered deceptively (D) and honestly (H). Previous DDP studies with the electrodermal SCR as the dependent variable have yielded the basic increase in responding to D relative to H questions (D > H), and have indicated that this effect is probably not due to cognitive factors such as differential retrieval difficulty, and is also relatively unaffected by motivational factors. To test the notion that the D > H effect does not represent genuine deception because of the elimination of the element of choice in the DDP, the present study varied, between two groups of 16 subjects, the degree to which subjects could choose which questions they would answer deceptively. If choice were necessary, or even important, for the differentiation-of-deception phenomenon, the D > H effect should have been greater in the free-choice condition, but the (nonsignificant) trend was in a direction opposite to this prediction. Another orthogonally-varied, between-subject manipulation, was the relative frequency of D and H items. The basic electrodermal D > H phenomenon, including the curious lack of response habituation during the session, has now been duplicated over a variety of conditions, but the mechanisms underlying the phenomenon are far from being well understood.