The effect of trait anxiety on the generalisation of fear acquisition and extinction

Abstract

Fear generalisation refers to the spread of fear to novel situations. Recent evidence has suggested that over-generalisation of fear is a pathogenic marker of anxiety disorders. Given that trait anxiety has been widely accepted as a vulnerability factor for developing an anxiety disorder, the current thesis aimed to examine whether trait anxious individuals show over-generalisation of fear like their clinical counterparts. Using a continuous perceptual dimension, the first experiment (Chapter 5) identified various generalisation gradients, which aligned logically with participants’ reported rules. Trait anxious individuals showed over-generalisation of fear to the novel test stimuli, but this pattern was only observed among those who failed to identify a clear rule. The following experiments (Chapter 6) further examined fear generalisation to objects that were conceptually related to the threat cues. Trait anxious individuals did not show more fear to novel exemplars that had clear categorical membership and therefore clear threat value. However, they showed more fear to novel exemplars that could be classified in both threat and safe categories, that is, exemplars with ambiguous threat value. The results supported the notion of threat appraisal bias under ambiguous threat among trait anxious individuals. The experiments in Chapter 7 examined the effect of trait anxiety on the generalisation of extinction learning along a blue-green stimulus dimension. Participants who received a generalisation stimulus (GS) in extinction showed an increase in conditioned fear to the original conditioned stimulus (CS) or to another novel GS in test. Conversely, this pattern was not found in those who received standard extinction with the CS. No trait anxiety effect was observed in the generalisation of extinction learning, however, trait anxious individuals showed slower fear extinction to the CS, but not to a GS. In summary, the present work suggests that over-generalisation of fear and resistance in fear extinction may be a special case of the more general principle that trait anxiety is associated with excessive threat appraisal under conditions of ambiguity. It also highlights the importance of higher-order cognitive processes in human fear generalisation. The current findings have important clinical implications. Specifically, they suggest the importance of targeting cognitive reappraisal and strategies that reduce situational ambiguity in clinical treatments.