Choice behavior in a discrete-trial concurrent VI-VR: A test of maximizing theories of matching

Rats were trained on a discrete-trial procedure in which one alternative (VR) was correlated with a constant probability of reinforcement while the other was correlated with a VI schedule which ran during the intertrial intervals and held the scheduled reinforcer until they were obtained by the next VI response. Relative reinforcement rate was varied in series of conditions in which the VR schedule was varied and in series in which the VI was varied. Choice behavior was described well by the generalized matching law, although moderate undermatching occurred for all subjects. Contrary to the predictions of molar maximizing (optimality) theories, there was no consistent bias in favor of the ratio alternative, and the sensitivity to reinforcement allocation was not systematically affected by whether the ratio or interval schedule was varied. The results were also contrary to momentary maximizing accounts, as there was no correspondence between the probability of a changeover to the VI behavior and the time since the last response to the VI alternative. Neither variety of maximizing theory appears to provide a general explanation of matching in concurrent schedules.