Punishment and dynamic choice: Assessment of the direct-suppression model.

The effects of punishment rate on response allocation were investigated using a choice procedure where relative reinforcement rates changed rapidly within session. Predictions from a modified version of the direct-suppression model were tested in two separate experiments. In both experiments, sessions were composed of seven unsignaled components, each programming a different reinforcement ratio. In Experiment 1, equal punishment rates were superimposed on the schedule of reinforcement for both responses and absolute punishment rates increased across blocks of sessions. Punishment increased preference for the richer schedule of reinforcement, but the degree of the preference shift was not a function of absolute punishment rates. In Experiment 2, unequal punishment rates were superimposed on the schedules of reinforcement for both responses and relative punishment rates changed across blocks of sessions. Response allocation shifted away from the richer punishment schedule creating a bias toward the option associated with less frequent punishment. The results from both experiments challenged the predictions of the direct-suppression model. Furthermore, fits of the generalized matching law to the data indicated that superimposition of equal or unequal punishment schedules on responses maintained by unequal reinforcement schedules differentially affect the values of sensitivity and bias.