Abstract:

The suggestion of individual differences in fear conditioning has been put forward as a potential etiological factor for the development of anxiety disorders. Previous studies mostly focused on investigating the differences in fear acquisition and extinction comparing anxious and non-anxious individuals, and different theories were developed for possible explanations. However, to provide evidence for a causal link between anxiety and fear conditioning, anxiety should be experimentally induced in healthy individuals. And to further understand the mechanism of anxiety and fear conditioning, evaluative conditioning should also be explored. An experiment was designed to test the impact of anxiety on fear conditioning. Forty-four healthy female participants were exposed to a psychological social stressor (or control condition) while subjective anxiety was measured, then all participants participated in a differential fear conditioning experiment consisted of habituation, acquisition, and extinction phases while subject US-expectancy was rated online. Two simple geometrical figures served as CS+ and CS?, and a 4-sec female scream as US. Each CS+ was paired with a US during the acquisition phase. To measure evaluative conditioning, participants were required to rate CS-valence at the end of each conditioning phase. The results showed that exposure to the stressor increased state anxiety. During acquisition, state anxiety inhibited discriminative conditioning between CS+ and CS?. Specifically, the anxiety group exhibited lower subjective US-expectancy ratings for CS+, but higher subjective US-expectancy ratings for CS? compared to control group. At the phase of extinction, state anxiety led to a deficit in extinction learning. The impact of state anxiety was also found in evaluative conditioning. The anxiety group showed more negative valence ratings for CS compared to control group in habituation and extinction phases. The results of this study support the theory, which identifies the failure to inhibit fear responses in the presence of safety signals (a CS?) in anxiety individuals. The results suggest that anxiety hinders the individuals’ ability to distinguish between safe and unsafe signals, and in turn impairs the adaptive response to threatening stimulus in a changeful environment. The results also show that anxiety attenuates the normal recovery process from aversive experiences, which indicates that individuals in an anxiety state would need more extinction trials (or exposure session) than individuals in a neutral emotional state. In addition, the relation between US-expectancy and CS-valence suggests that successful exposure therapy should be more focused on the changing of the individuals’ negative evaluation reactions of CS.

Key words: fear conditioning, state anxiety, evaluative conditioning