Response-reinforcer dependency location in interval schedules of reinforcement

In five experiments we studied the effects on pigeons' key pecking of the location of four or more successive response-dependent reinforcers imbedded in a schedule arranging otherwise response-independent reinforcers. In Experiment 1, high local response rates early in the session were extended farther into the session as the number of response-dependent reinforcers at the beginning of the session increased. A block of four successive response-dependent reinforcers then was scheduled at the beginning, middle, or end of the session (Experiment 2) resulting in higher local response rates at those times in the session when the response-dependent reinforcers were arranged. When placed in random locations in successive sessions (Experiment 3), uniform local rates occurred throughout the session. In Experiments 1, 2, and 3, delivery of the remaining response-independent reinforcers was precluded until the response-dependent reinforcers were collected. Experiment 4 was similar to Experiments 1 and 2, except that all response-independent reinforcers occurred irrespective of whether the response-dependent reinforcers had been collected. This yielded results similar to those obtained in the first two experiments. In Experiment 5, responding early in the session had no consequence other than allowing access to the schedule of response-independent food delivery. As in the first experiment, local rates generally were higher early in the session. The results indicate that the location of response-reinforcer dependencies precisely control behavior and that such effects often are not captured by descriptions of behavior in terms of overall response rates.