Optimizing exposure therapy: Strengths and limitations of the extinction model
Exposure involves the (repeated) confrontation with fear-eliciting stimuli or situations in the absence of the feared outcome and is a key-component in the treatment of clinical fears and anxiety. Several meta-analyses have demonstrated large effect sizes and response rates of exposure treatment. However, these effects are not always maintained in the long-term, leaving room for the further enhancement of clinical treatment. The first part of this dissertation (Chapter 1) introduces and evaluates fear conditioning as a laboratory model for the acquisition and treatment of clinical fears and anxiety. In addition, we discuss how recent developments in learning theory can address some of the frequently heard critiques on simple fear conditioning.
In the second part of this dissertation, we report on empirical studies that focus on optimizing exposure treatment. In Chapter 2 and 3, respectively the type and order of stimuli presented during extinction were manipulated. In Chapter 2, we investigated whether manipulating the typicality of the extinction stimulus can attenuate return of fear. We found that using a generalization stimulus during extinction that is a typical exemplar of the feared category resulted in less fear responding to a new exemplar of that feared category compared to using an atypical exemplar. In Chapter 3, we developed a fear extinction procedure to compare the outcomes of a hierarchical versus random approach of exposure. A set of morphs between the danger (CS+) and safety (CS-) cue were presented in a hierarchical order (i.e., starting with the CS-, then the morph most similar to the CS-, followed by the morph most similar to that one etc., until reaching the CS+) versus in a random order. No differences between the hierarchical and random approach were found in fear responding as tested one day later.
In Chapter 4 and 5 we explore the effects of manipulations of expectancy violation (i.e., the mismatch between the expected and actual outcome), which according to inhibitory learning theory (ILT) drives inhibitory learning during exposure and long-term fear reduction. In Chapter 4, we investigated the role of expectancy violation in virtual reality exposure therapy (VRET). Both the experimental and correlational analyses failed to confirm that expectancy violation predicted treatment outcome. In Chapter 5, the effect of providing safety information before extinction – similar to types of psychoeduction before exposure – was investigated. ILT predicts that providing this type of information interferes with subsequent expectancy violation during extinction. We could not confirm that providing safety information was detrimental for the generalization of fear reduction to another context.
In the third part of this dissertation (Chapter 6), we reflect on the extinction procedures that we used in the empirical chapters and evaluate the validity of extinction research in providing insights on (how to conduct) clinical exposure therapy. Finally, our findings and conclusions are embedded in a more general discussion of some of the strengths and challenges of ILT.