Skin Conductance Responses to Stimulus “Energy” Decreases Following Habituation

Two experiments are reported in which a reduction in tone intensity or duration followed habituation. Experiment I, which employed 120 subjects, assessed the effects of type of stimulus change (intensity or duration) and trial of change (trial 5 or trial 22) on orienting response (OR) recovery. Experiment II employed 131 subjects, and examined the effects of reduction of stimulus intensity on trial 22 or after subjects reached a predetermined habituation criterion. Experiment I demonstrated OR reappearance following the offset of a shortened stimulus. The combined findings of Experiments I and II suggest that the effects of reducing stimulus intensity depend on when the change is made. In Experiment I, reducing stimulus intensity on trial 5 led to a significant decrease in OR magnitude. In Experiment II, increases in OR magnitude were produced by reducing stimulus intensity either after reaching a criterion or after 21 habituation trials. These findings suggest a Sokolovian view of the development of the generalization gradient of habituation. Results also revealed large individual differences in responding to the stimulus change in Experiment II. Multiple regression analyses of these data were therefore conducted, which allowed two further conclusions to be drawn: First, initial electrodermal state can be used to predict responding on the stimulus change trial. Second, with long habituation training (21 trials), the role of the initial state variables diminishes while other variables representing change over the experimental session become more prominent in predicting responding to stimulus change.