Prevailing models of exposure therapy for phobias and anxiety disorders construe level of fear throughout exposure trials as an index of corrective learning. However, the evidence, reviewed herein, indicates that neither the degree by which fear reduces nor the ending fear level predict therapeutic outcome. Developments in the theory and science of fear extinction, and learning and memory, indicate that ‘performance during training’ is not commensurate with learning at the process level. Inhibitory learning is recognized as being central to extinction and access to secondary inhibitory associations is subject to influences such as context and time, rather than fear during extinction training. Strategies for enhancing inhibitory learning, and its retrieval over time and context, are reviewed along with their clinical implications for exposure therapy and directions for future research.
learning and memory on the one hand, and models and methods of exposure therapy for phobias and anxiety disorders on the other hand. The argument to be made is that the customary reductions in reported fear and physiological arousal throughout exposure therapy are not evidence for corrective learning. Therapeutic efforts are better directed towards toleration of distress within a structure that enhances the consolidation and retrievability of exposure-based inhibitory learning over context and time. The goal is not to question the necessity of exposure therapy for phobias and anxiety disorders; it is already well established that phobias and anxiety disorders respond positively to approaches such as cognitive therapy (e.g., Norton & Price, 2007) and medications (e.g., Roy-Byrne & Cowley, 2002) as well as exposure-based therapies. Rather, the goal is to update conceptualizations of the mechanisms underlying exposure therapy.
The first of two lines of basic science research from which we draw is extinction learning, since the extinction of conditioned fear can be viewed as a laboratory analogue for exposure therapy (Bouton, Mineka, & Barlow, 2001; Davey, 1997; Eelen, Hermans & Baeyens, 2001; Mineka, 1985).1 Knowledge of the mechanisms underlying extinction learning, and the resultant conditions that facilitate or hamper extinction learning, may help to sharpen exposure treatments and maximize outcomes in both the short and long run (i.e., relapse prevention). Indeed, extinction learning has served as the explicit model of behavior therapy for phobias for many years (see Eelen & Vervliet, 2006), and extinction-like processes continue to be emphasized, albeit in ways that lag behind recent advances.
The second line of basic science research pertains to learning and memory, since what is learned throughout exposure therapy is intended to be remembered in different places and at later points in time once exposure therapy is over. The evidence pertaining to the retrieval strength of learning, presented cogently in the ‘new theory of disuse’ (Bjork & Bjork (1992) and Bjork & Bjork (2006)), has relevance to the long-term outcomes from exposure therapy. Naturally, this line of research overlaps with the science of extinction learning.
Before discussing these advances, we overview the prevailing model of exposure therapy for phobias and anxiety disorders, which purports that fear levels throughout exposure therapy are reflective of learning and are critical to overall therapeutic outcome.
Reliance upon fear levels throughout exposure therapy as an index of learning is not only lacking empirical support, but assumes that performance during ‘instruction’ is a reliable index of learning; an assumption that is not supported by learning and memory research. Inhibitory processes are now recognized as being central to extinction learning, and evocation of such processes at the time of re-exposure to a previously feared stimulus largely shapes the level of fear, regardless of how much fear was expressed during or at completion of extinction training. Evocation of inhibitory associations is instead influenced by variables such as context and time.
Furthermore, reliance upon fear reduction as an index of corrective learning is at odds with the importance of toleration of fear. Thus, in the paper, we argue for moving away from immediate fear reduction and toward fear toleration as a primary goal of exposure therapy. Also, we conceptualize exposure therapy as reshaping memory, forming new, secondary learning and involving brain regions that contribute to such learning. We posit that exposure efforts should be oriented towards facilitating inhibitory learning, or ways of developing competing, non-threat associations, at both propositional and automatic levels, and ways of enhancing the accessibility and retrievability of those associations over time and in different contexts. We have outlined methodologies for consolidation and retrievability of exposure-based learning that are derived from basic science of learning and memory, and extinction research, some of which have been investigated and some awaiting such investigation.
