Avoidance behavior triggers return of fear during extinction learning

Avoidance behavior is thought to contribute to the development and maintenance of anxiety disorders. Previous research has shown that avoidance preserved threat beliefs by blocking extinction learning. In this study, we investigated the effect of continued intermittent avoidance behavior during extinction learning on physiological conditioned responses. We used an instrumental avoidance procedure combined with Pavlovian fear conditioning. Fear-potentiated startle (FPS) was assessed to determine conditioned responding during acquisition and extinction. The critical test was between a CS during which participants were able to press a button to avoid the US (electric shock) (CS+A) and a CS where this was not possible (CS+U). During acquisition, contingencies between both CS+’s and the US were trained with a 50% reinforcement schedule. Then, the avoidant response during CS+A trials, only when the visual cue was available, was acquired. During extinction, avoidance trials were interjected between blocks of trials to test their effect on extinction. Across blocks, participants showed less successful extinction learning of CS+A in comparison to CS+U. An analysis of FPS across trials within blocks during extinction indicated a return of FPS in CS+A trials directly following an avoidance trial. These findings indicate that continued avoidant behavior during extinction is detrimental to successful extinction. Moreover, being reminded of the avoidance response reinstates FPS specifically during the CS previously associated with avoidance. The mechanism behind this effect has yet to be determined.