Post-reinforcement pauses and response rate of monkeys on a two-hand fixed-ratio schedule.

Fixed-ratio behavior of monkeys was analyzed separately for two hands. While one hand responded on the fixed-ratio schedule the other performed a holding response and the function of the hands changed in alternate ratio runs. After performance was stable on the fixed ratio (70 responses, two monkeys; 100 responses, two monkeys, 120 responses, two monkeys) 90 sessions of further training equalized post-reinforcement pauses and the mean interresponse time of the two hands. Hand preference in reaching for food remained unchanged. Then, the fixed-ratio requirement was changed (a) in small sequential steps, (b) in two large steps, and, (c) within sessions alternating two runs at a high ratio with two runs at a low ratio. The mean duration of post-reinforcement pauses was correlated with a fixed ratio maintained throughout a session but single pauses were neither controlled by the immediately preceding nor by the following ratio run when a cue to its length was available. The mean interresponse time was insensitive to changes in fixed ratio. The fixed-ratio performance was generally similar to that of pigeons and rats.