Effects of US habituation following skin-conductance response conditioning: Support for a Pavlovian S-S position and a habituation account of nonmonotonic acquisition functions

Abstract

After 48 subjects were given differential skin-conductance response (SCR) conditioning (six trials each with CS+ and CS−) with a 4-sec CS+US interval and a 100-dB white noise as US, they were divided into three equal groups in a treatment phase that comprised the following conditions for the three groups. For the conditioning group, there were 70 trials of the US paired with CS+ (i.e., CS+US conditioning trials) interspersed with 70 CS− trials (i.e., unpaired CS trials for differential conditioning), at a mean intertrial interval of 20 sec; for the habituation group, the 70 noise USs were presented at the same time as those for the conditioning group, but no CSs were given; for the control group, the conditions of the habituation group were duplicated, except that another strong stimulus, a 1.5-mA shock, replaced the noise US. Following the treatment phase, the effects of the different treatments on differential conditioning were assessed in a final test phase by presenting five CS+ and five CS− stimuli. The initial acquisition stage produced significant and equal SCR differentiation in all three groups, and all three treatments resulted in total habituation of the SCR to the aversive stimulus. Differential conditioning was totally absent during the test phase, not only in the conditioning but also in the habituation group; it was preserved, however, in the control group, which had been (totally) habituated to a stimulus modally different from the US. It is argued that these results support an S-S over an S-R interpretation of conditioning, and therefore provide an empirical extension of the pattern of results reported earlier in response-suppression paradigms wherein the mediational CRs are not directly observed. Also, the results suggest that US habituation is responsible for the nonmonotonic acquisition functions that are often seen in human differential SCR conditioning.