Acquisition, extinction, and spontaneous recovery as a function of percentage of reinforcement and intertrial intervals.

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Abstract
White rats were run in a 4-ft. alley runway with running time taken as the response measure. Four variables were manipulated factorially; 15-sec. and 2-min. intertrial intervals in acquisition, 50% and 100% reinforcement, 15-sec. and 2-min. intervals in extinction, and 1-, 5-, 10-, and 60-min. delay intervals before a spontaneous recovery test. The results showed During acquisition, running times were significantly faster for 100% reinforcement than for 50% reinforcement. Following 50% reinforcement, running times in extinction were significantly faster than following 100% reinforcement. The 15-sec. "massed" acquisition interval led to faster running times in extinction than did the 2-min. "spaced" interval. The massed extinction interval led to significantly slower running times for the last 15 extinction trials than did the spaced interval, although this difference did not attain statistical significance for all 30 trials. Partial reinforcement led to significantly greater resistance to extinction if followed by a spaced extinction interval than if followed by massed. Interaction between percentage of reinforcement and the acquisition interval was not significant. Spontaneous recovery was found to be a significant function of the postextinction delay interval. Spontaneous recovery was significantly greater following a massed acquisition interval than a spaced. Relevance of some of these findings to important theoretical notions was indicated.
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