Special Issue Registered Report: Intentional suppression as a method to boost fear extinction

Fear is a universal experience and fuels our response to cope with threat. Persistent fear, after the threat is no longer present, is a central symptom seen in a number of clinical conditions. Exposure therapy, the most common treatment to target fear, aims to reduce fear responses through repeated, controlled exposures to feared situations in the absence of the negative consequence, thus promoting extinction. However, this treatment is by no means effective for all people. This may be due to impaired extinction and the underlying mechanism of inhibitory retrieval. Intentional memory suppression has been shown to be a promising strategy to enhance this underlying inhibitory mechanism. We employed a newly developed paradigm combining aspects of the Think/No-Think procedure with fear extinction. Sixty-eight healthy participants learned 36 strong naturalistic reminder objects for aversive scenes. After learning, half of the objects were paired with an aversive scream (unconditioned stimulus/US). During the extinction phase, while viewing the objects, participants were instructed to repeatedly retrieve (Think instruction) or suppress (No-Think instruction) the corresponding scenes, or passively view the objects (View instruction). We hypothesised that intentional suppression would boost fear extinction, as shown by a reduced US expectancy to threat-conditioned objects that had been subject to memory suppression during extinction training compared to threat-conditioned objects that were passively viewed. Both intentional memory suppression and passive viewing reduced negative valence for upsetting scenes over time. Contrary to our hypothesis, the results indicated that intentional suppression (No-Think instruction) was not more effective in reducing US expectancy and fear than standard extinction (View instruction). Future research should address the limitation of self-reports by using physiological measures and examine whether intentional suppression may impact fear recovery and generalization following a longer extinction delay. The current findings show that, although intentional suppression can support inhibition of memories and reduce their valence, it may not be as effective as standard extinction methods in diminishing fear responses.