Comparison of Short-Many and Long-Few Presentations on the Extinction of Conditioned Fear: Implications for Exposure Therapy

Abstract

Study objective: To compare the efficacy of two techniques of exposure therapy for acquired fear: presenting a short-duration stimulus many times vs. presenting a long-duration stimulus a few times, using an animal model. Design: Short-many and long-few presentation conditions were compared within subjects. Setting: The experiment was conducted with individual boxes for each subject. Subjects: Seven male Wistar rats deprived of water for 22 hours. Independent variables: After pairing each of two 10-second pure tone stimuli (high-pitched and low-pitched) with a shock, the extinction phase was initiated, during which the duration and number of each tone per session were as follows: 4 presentations of 5 seconds each or 1 presentation of 20 seconds, allocated to the two tone stimuli. The duration of each stimulus in the post-extinction test was 10 seconds. Measure: Licking responses (licking counts) in each daily 5-minute session were recorded via an electric circuit, and the change in licking responses following each of the tones was measured using suppression rate as an index of fear. Results: Fear responses occurring after the extinction phase were smaller for the tone that had been presented many times for short durations compared to the tone that had been presented a few times for long durations. Conclusion: When treating acquired fear using exposure therapy, many presentations for short times may be preferable to few presentations for a long time.