A test of the effectiveness of the differential-reinforcement-of-low-rate schedule.

Pigeons and rats were used in a yoked-control design that equated the reinforcement distributions of differential-reinforcement-of-low-rate and variable-interval schedules. Both a between-subjects design and a within-subjects design found response rate higher for the variable-interval schedule than for the differential-reinforcement-of-low-rate schedule, thus demonstrating the effectiveness of the differential-reinforcement-of-low-rate contingency. The interresponse-time distributions were unimodal for all subjects under the variable-interval schedule and bimodal for pigeons under the differential-reinforcement-of-low-rate schedule. The interresponse-time distributions for rats under the differential-reinforcement-of-low-rate schedule were also bimodal in three of four cases but the height of the modes at the shorter interresponse times were small in both absolute value and in relation to the height of the modes at the shorter interresponse times of the pigeons' distributions.