The spread of fear: symbolic generalization mediates graded threat-avoidance in specific phobia

Overgeneralization of fear and threat-avoidance represents a formidable barrier to successful clinical treatment of anxiety disorders. While stimulus generalization along quantifiable physical dimensions has been studied extensively, less consideration has been given to symbolic generalization, in which stimuli are indirectly and arbitrarily related. The present study examined whether the magnitude and extent of symbolic generalization of threat-avoidance and threat-beliefs differed between spider-phobic and nonphobic individuals. Initially, participants learned two sets of stimulus equivalence relations (A1 = B1 = C1; A2 = B2 = C2). Next, one cue (B1) was established as a conditioned stimulus (CS + ; threat) that signalled onset of spider images and prompted avoidance, and another cue (B2) was established as a CS- (safety cue) that signalled the absence of such images. Subsequent testing showed that phobics compared to nonphobics exhibited greater symbolic generalization of threat-avoidance to threat cues A1 and C1 (indirect CS+ threat cues related via symmetry and equivalence, respectively), while all individuals showed nonavoidance to indirect safety cues A2 and C2. The enhanced symbolic generalization of threat-beliefs and avoidance behaviour observed in spider phobics warrants further investigation.