Differential aversive outcome expectancies for high- and low-predation fear-relevant animals.

There is now considerable evidence that phobic responding is associated with a bias towards expecting aversive or traumatic outcomes following encounters with the phobic stimulus (e.g. Behavioural Brain Sci. 18 (1995) 289-325; Phobias: A Handbook of Theory, Research and Treatment. Wiley, Chichester, 1997). In terms of conditioning contingencies, this can be described as a bias towards expecting an aversive unconditioned stimulus (UCS) following a phobic conditioned stimulus (CS). The disease-avoidance model of animal fears (Anxiety Res. 4 (1992a) 314; Matchett and Davey, 1991) suggests that common animal fears may be mediated by at least two kinds of selective associations: (1) a bias towards expecting physically harmful consequences associated with predatory animals, and (2) a bias towards expecting disgust or disease-relevant consequences associated with animals that are fear-relevant (FR) but normally physically harmless. The present study investigated this model of selective associations by comparing the UCS expectations elicited by high-predation FR, low-predation FR and safe (fear-irrelevant) animals. The results indicate that high-predation animals are selectively associated with a pain relevant UCS, whilst low-predation animals are selectively associated with a disgust-relevant UCS. Safe animals were not strongly associated with either class of UCS. These findings provide evidence for a possible associative mechanism by which changes in nonspecific levels of disgust sensitivity may directly affect levels of fear to low-predation FR animals.