Date of Award


Degree Name

Doctor of Philosophy



First Advisor

Dr. C. Richard Spates


It is widely accepted that for exposure-based therapies to be effective feareliciting stimuli must be presented continuously until there is a marked decrease in the client's anxiety (e.g., Eysenck, 1979; Foa & Kozak, 1986). However, an emerging body of research (cf. Seim, Waller, & Spates, 2010) suggests that a massed series of very brief exposures (< 150 sec) may be effective in the extinction of fear responses. The present study was designed to compare the efficacy and acceptability of two one-session treatments for animal phobias: one that utilized continuous, uninterrupted periods of exposure to a feared animal (Prolonged Exposures) and the other that utilized a massed series of brief (5-120 sec) exposure trials (Dosed Exposures). 24 adults (7 males, 17 females) between the ages of 18 and 57 years (M = 23.6) participated in this study. Each individual met DSM-IV criteria for a diagnosis of snake phobia or spider phobia. Participants were randomly assigned to one of two the two interventions. Both treatments required participants to gradually enter a room, approach, and eventually hold a live ball python or tarantula. Results from mixed model (between x within subjects) analyses of variance showed that the Dosed Exposure treatment performed equally well to Prolonged Exposures at decreasing behavioral avoidance, feelings of anxiety, perceptions of threat, and phobiaspecific cognitions from pre-treatment to post-treatment, and these gains were maintained at one-week follow-up. Although participants receiving Prolonged Exposures reported lower ratings of within-session anxiety, participants in the Dosed Exposure group had lower rates of treatment dropout, better compliance with procedures, and fewer safety-seeking behaviors during the treatment. These findings suggest that, contrary to popular belief, brief exposure trials can be effective in the extinction of phobic responses under certain conditions.

Access Setting

Dissertation-Open Access