UCS expectancy biases in spider phobics: underestimation of aversive consequences following fear-irrelevant stimuli

This paper reports the results of two studies investigating judgements made by spider phobics about the potential threatening consequences (unconditio ned stimulus, UCS, expectancies) associated with their phobic stimulus, fea r-relevant (FR) stimuli, and fear-irrelevant (FI) stimuli. Using a 'thought experiment' UCS expectancy paradigm, the studies reported found that (1) s pider phobics reported significantly higher UCS expectancies to spider stim uli than nonphobics, (2) spider phobics consistently underestimated the pro bability of aversive consequences following FI stimuli and (3) this underes timation of UCS expectancies to FI stimuli in phobics was not the result of a contrast effect resulting from sequential FR and FI judgements. This dif ferential effect may have important implications for the kind of mechanism which mediates judgements about phobic consequences. These findings suggest that the dimensions on which phobic stimuli are categorised may be 'stretc hed' in the case of phobics and that this gives rise to the comparative und erestimation of threat associated with FI stimuli but also makes phobics mo re vulnerable to acquiring other phobias. (C) 2000 Elsevier Science Ltd. Al l rights reserved.