Electrodermal and cardiovascular responses to phobia-relevant stimuli in a trace conditioning paradigm: Effects of instructions

The present study concerns itself with the hypothesis that the preparedness phenomenon demonstrated by Ohman and co-workers (1985) is non-cognitive in nature, i.e., is not dependent upon subjects deliberately focusing their attention on the contingency between a phobia-relevant conditioned stimulus (CS+) and shock. In order to test this hypothesis, a trace conditioning experiment was carried out in which one group of subjects saw a phobia-relevant CS+ and a second group saw a neutral CS+. During acquisition, the former group was confronted with the sequence phobia-relevant CS+ (slides of snakes or spiders)/shock/non-reinforced, neutral CS- (slides of mushrooms or flowers), while the latter group was confronted with the sequence neutral CS+/shock/phobia-relevant CS-. Within each group, half of the subjects received that stressd the CS+/shock contingency ('forward' instruction), while the other half was asked to pay special attention to the CS-, which always followed shock ('backward' instruction). The experiment consisted of 6 habituation, 12 acquisition, and 24 extinction trials. Both skin conductance responses (SCRs) and heart rate responses (HRRs) were measured. SCRs were found to extinguish more slowly in subjects who had received a 'forward' instruction than in subjects with a 'backward' instruction. however, there was no resistance to extinction of the conditioned SCRs in subjects who saw a phobia-relevant CS+ and received a 'backward' instruction. Thus, the delayed extinction of conditioned SCRs was not dependent upon the phobia relevance of the CS+, but rather upon the amount of attention that subjects were asked to pay to the CS+/shock contingency. For HRRs, a less comprehensive picture emerged, with phobia-relevant CS+s eliciting accelerative responding during habituation, a small deceleration during acquisition, and no significant changes from baseline during extinction. Results are related to other recent studies that have yielded contradictory evidence for the alleged non-cognitive nature of the preparedness phenomenon.