Choice and response contingencies.

Two experiments investigated the extent to which response contingencies influence the choice between two schedules of reinforcement by exposing pigeons to a concurrent-chains procedure in which reinforcers in one terminal link were response-independent, and in the other terminal link, response-dependent. In Experiment 1, the pigeons were indifferent between an aperiodic, response-independent schedule and an aperiodic, response-dependent schedule that required a minimum rate of responding. This finding limits the generality of a required-rate contingency as a determinant of choice, which contingency had been previously demonstrated in a context of periodic reinforcement to evoke preference for an alternate schedule. In Experiment 2, the pigeons preferred a periodic, response-independent schedule to a periodic, response-dependent schedule that shared a feature with a required-rate schedule: there was a requirement to respond early in the interreinforcement interval, when responding produced reinforcement only later. The results of the two experiments suggest the following general interpretation: pigeons prefer a second schedule to the extent that the response contingencies of the first schedule must be satisfied during discriminable periods of nonreinforcement.