A preliminary resolution of the retention of distributed vs massed response prevention in rats

This study consisted of two experiments conducted to investigate the difference in efficacy and retention of distributed response prevention when compared to massed response prevention using an animal model of avoidance learning. The purpose was to obtain an estimate of the over-all treatment time for response prevention that begins to be affected by the treatment, either distributed or massed. In Exp. 1, 50 rats were given two trials of escape learning in a one-way black-white shuttle-box. Groups received response-prevention treatment or nontreatment in 9 1-min. distributed sessions or 1 9-min. massed session. Subjects were tested using a passive-avoidance paradigm immediately following treatment, 24 hours, and 720 hours (30 days) later. Analysis showed that with an over-all response-prevention time of 9 min., response-prevention treatment was effective in reducing avoidance behavior, that the effect was retained, and that there were no differences between distributed and massed groups. These results led to Exp. II in which 50 rats were exposed to the same training procedure as in Exp. I. These groups received response-prevention treatment or nontreatment in 12 15-sec. distributed sessions or one 3-min. massed session. Analysis of passive-avoidance testing immediately following treatment, 24 hr., and 720 hr. later showed that, when the over-all response-prevention time was 3 min., only groups with distributed treatment showed reduction of avoidance behavior and retention of the treatment effects. Since past studies have produced inconsistent findings in comparing distributed vs massed delivery of response-prevention treatment these two experiments are intended to serve as a preliminary resolution of the past differing results. When the over-all treatment time is longer than 3 min., there is no delivery of treatment effect. However, with 3 min. of over-all treatment time, distributed delivery was necessary to facilitate the treatment effects. Implications for animals and humans are discussed.