Response Rates on Variable-Interval Schedules: Sequential Interresponse Time Requirements and Reinforcement Rate

Abstract

Pigeons’ response rates on three different sized variable-interval (VI) schedules were determined with three different interresponse time (IRT) contingencies. When the VI schedule arranged a reinforcement, either a single IRT between 1.0 and 1.5 sec. was required to produce the reinforcer or, in other experimental conditions, two or three such IRTs in succession were required to produce the reinforcer. Under these IRT contingencies, the observed response rates were not related to reinforcement rates (size of the VI) in any obvious orderly way. When only the final IRT concluded by the response immediately preceding each reinforcement was required to be between 1.0 and 1.5 sec. duration, the mean emitted IRT usually was not between 1.0 and 1.5 sec. When the next back IRT also was required to be between 1.0 and 1.5 sec., the mean emitted IRT was very near or between 1.0 and 1.5 sec. Results suggest that a comprehensive account of VI responding which emphasizes IRT reinforcement should consider not only the duration of the IRT immediately preceding each reinforcement but also the IRTs of preceding responses.