Behavioral contrast in chained schedules

In each of two experiments, the rate of key pecking maintained by a variable-interval food reinforcement schedule was measured, first when that schedule was studied in isolation, and then when it was correlated with the second component of a two-component chained schedule. In the first experiment, the first component of the chained schedule was correlated with a fixed-interval schedule; in the second experiment it was correlated with a variable-interval schedule. In both experiments, behavioral contrast was demonstrated in the second component of the chained schedule. Compared to the rate of responding on the food-reinforcement schedule when it had operated in isolation, the rate of responding on the food-reinforcement schedule when it was correlated with the second component was higher, while the rate on the schedule of the first component was lower. The results are discussed with reference to the determinants of contrast.