Interactive Effects of Stimulus Probability and Significance on the Skin Conductance Response

The present study deals with the effects of stimulus significance and stimulus probability on skin conductance responses (SCRs). Eighty subjects (“informed” group) chose a numbered card, and 60 subjects (“uninformed” group) chose a blank card. All subjects were presented with a series of stimuli in the form of questions about numbers. The relative frequencies of the relevant (chosen) numbers were manipulated. The results showed expected effects of stimulus relevance and stimulus probability on SCRs. A more interesting result was an interaction of stimulus significance and relative frequency, meaning that the probability effect (greater responsivity to the less frequent stimulus) was stronger when the series of stimuli was comprised of relevant and neutral stimuli, than when two different neutral stimuli were used. This latter result was interpreted in terms of generalization of habituation. It was suggested that the relevance manipulation interferes with the generalization of habituation process.