Time limits for completing fixed ratios.

Two experiments investigated how the addition of time limits affected fixed-ratio behavior. In Exp. 1, pigeons obtained food only if they completed the ratio within a specified time after the end of the preceding ratio. In Exp. 2, they obtained food only if they took longer than a specified time. Failures to meet the time criteria produced brief timeouts. The times taken depended on the requirements in both experiments. In Exp. 1, progressively briefer time criteria resulted in faster ratios, and in Exp. 2, longer time criteria increased the time taken in each ratio. The pigeon's sensitivity to the temporal variable, a property of the entire period extending from the first opportunity to respond to the end of the ratio, indicated that performance involved a behavioral unit encompassing both the post-reinforcement pause and the responses comprising the ratio.