A Preliminary Investigation of Continuous and Intermittent Exposures in the Treatment of Public Speaking Anxiety.

INTRODUCTION Since the nascence of exposure-based interventions for the treatment of anxiety disorders in the mid 20th century, much research has been devoted to dismantling these interventions, investigating the manipulation of different parameters of the exposure, and determining which parameters are most essential. Numerous parameters have been investigated, such as the targeted modality of the exposure (i.e. imaginal vs. in vivo vs. analog stimuli), the presentation of these stimuli (i.e. graduated vs. immediate presentations), and the length of time between exposures (i.e. massed vs. spaced exposures). One variable that has been under-studied, however, is the optimal duration of exposure trials. It is commonly assumed that exposures must be delivered in a protracted, continuous fashion until a decrement in anxiety is achieved (Foa & Kozak, 1986). However, empirical findings to support this notion have been mixed. Extinction of Conditioned Avoidance The earliest work on the optimal duration of exposure trials came from research using animal models of anxiety using the conditioned avoidance paradigm. This design involves an avoidance-training phase, where subjects learn to run or jump to another area of a chamber in the presence of a conditioned stimulus (CS) (i.e. a light, a tone, or a buzzer) which has been paired with an unconditioned stimulus (US) (i.e. a footshock) until they become proficient at avoiding the US by responding in the presence of the CS alone. The avoidance-training phase is then followed by an extinction phase, involving the presentation of the CS in the absence of the US until the CS no longer elicits the avoidance response. Several studies have investigated the efficacy of differing exposure lengths on the extinction of conditioned avoidance, using this paradigm. Research by Polin (1959) found that one 100 sec trial of exposure produced more rapid extinction than twenty 5 sec exposures with response prevention. Though this provided evidence for prolonged trials over brief trials, the interpretation was confounded by the use of response prevention in only the brief exposure condition. To control for response prevention, Shearman (1970) compared 100 sec presentations of a CS with and without response prevention against twenty 5 sec trials, with and without response prevention. Shearman found no differences between the lengths of the exposure trials and concluded that response prevention, not CS duration, was the critical variable. A follow-up study by Berman and Katsev (1972) which replicated the methodology of Shearman (1970) found that shorter durations were actually more effective than one prolonged duration. And further research by Schiff, Smith, and Prochaska (1972) and Martasian, Smith, Neil, and Reig (1992), found that total duration time to the CS was the crucial variable in the extinction of conditioned avoidance, regardless of whether the individual exposures lasted 5 sec or 24 min in length. Extinction of Conditioned Fear While the conditioned avoidance paradigm offers a directly observable method for studying the reduction in physical avoidance, it does not permit an examination of extinction of the affective components of anxiety. When avoidance behaviors decrease in the presence of the CS after exposure training, it is assumed that the CS no longer elicits fear and no longer acts as a reflexive conditioned establishing operation (CEO-R) (see Michael, 1993) for the avoidance response. However, as Lang (1979) has argued, anxiety comprises three individual response systems (i.e. physiological, behavioral, and cognitive/affective) that are not always concordant. It has further been argued that fear in the presence of the CS often persists, despite the suppression of overt avoidance (Shipley, 1974). In order to examine the extinction of the private events/affective components of anxiety, the conditioned fear paradigm was developed. …