Desensitization as an habituation phenomenon. I. Stimulus intensity as determinant of the effects of stimulus lengths

Enhancing Inhibitory Learning: The Utility of Variability in Exposure

Exposure therapy has strong empirical support as a treatment for anxiety and related disorders, yet not all participants see clinically meaningful reduction in symptoms, and some experience return of fear. In this review, we examine the theoretical models of exposure therapy, from early precursors to the contemporary inhibitory learning model. The inhibitory learning model is applied to examine one potential method of improving outcomes in exposure therapy: increasing variability in the progression of the exposure hierarchy. We explore mechanisms that support the use of variability in exposure, including the violation of expectancies to enhance learning. In addition, the role of intolerance of uncertainty in anxiety is examined; variable exposure therapy could target this transdiagnostic mechanism in anxiety and related disorders. Suggestions for future research are then offered.

The conditioning model of neurosis

The long-term persistence of neurotic symptoms, such as anxiety, poses difficult problems for any psychological theory. An attempt is made to revive the Watson-Mowrer conditioning theory and to avoid the many criticisms directed against it in the past. It is suggested that recent research has produced changes in learning theory that can be used to render this possible. In the first place, the doctrine of equipotentiality has been shown to be wrong, and some such concept as Seligman's “preparedness” is required, that is the notion that certain CS are biologically prepared to be more readily connected with anxiety responses than others. In the second place, the law of extinction has to be amended, and the law of incubation or enhancement added, according to which the exposure of the CS-only may, under certain specified conditions, have the effect of increasing the strength of the CR, rather than reducing it. The major conditions favouring incubation are (1) Pavlovian B conditioning, that is a type of conditioning in which the CR is a drive; (2) a strong UCS, and (3) short exposure of the CS-only.

Effects of Short Exposures to Phobic Material upon Subsequent Phobic Responses

Two theories have been advanced to explain the paradoxical increase in fear and avoidance seen after short unreinforced exposures to phobic stimuli. Incubation theory (Eysenck, 1968) and sensitization theory (Watts, 1971) are similar with regard to the conditions specified for enhancement of such responses. However, an incubated response is seen as specific to the CS in question, whereas sensitized responsiveness is a more generalized process. Subjects were either exposed or not exposed to a feared stimulus (cockroaches), and were then administered generalization tests to the same stimulus or to a non-feared stimulus (toad). Measures of subjective anxiety, behavioural avoidance and physiological activity were taken. No evidence was found for the enhancement phenomenon to either phobic material or non-feared material. The phenomenon does not appear to be a reliable one.

The effects of distraction during exposure to phobic stimuli

Theoretical conceptualizations regarding the role of attentional focus during exposure-based treatments for fear and anxiety suggest that distraction interferes with the mechanisms required for fear reduction, typically by preventing emotional and/or cognitive processing of the phobic stimulus and response. The present discussion reviews the current literature and demonstrates the paucity of empirical evidence supporting such notions. Seemingly conflicting findings are integrated upon close examination of the various qualitative dimensions of the distracters employed. These characteristics, which differed substantially across studies, include the nature of the attentional demand posed by the distracter (e.g. cognitive vs sensory demand) as well as the distracter's affective quality (e.g. neutral vs relaxing). The effects of differing dimensions of distraction on fear reduction, in addition to interaction with aspects of the exposure situation, are discussed. The need for further investigation of the qualitative dimensions of distraction, including their operational specification, is recognized. Finally, recommendations for future research are made.

Desensitization as an habituation phenomenon. II. Studies on interstimulus interval length

Predictions about the effect of interstimulus intervals (ISIs) in desensitization were made from the habituation model and tested with a series of Ss, each serving as his own control. Strong items desensitized faster with long ISIs, though weak items were not affected. No effects on long-term response decrements were found. A second experiment examined an interpretation of the stimulus-length effect in desensitization in terms of an extension of the recovery period between stimulus onsets. The results permitted rejection of the hypothesis.