Reinforcer Rate and Stimulus Control in Discrimination Reversal Learning

Nine subjects with mental retardation were trained with a fading procedure to perform two-choice simple-discrimination tasks. Immediately after meeting a learning criterion, discrimination reversals were trained within the same sessions, also with the fading procedure. Two 10- or 16-reversal conditions were compared within subjects: High, in which all correct responses for the initial discrimination were followed by reinforcers, and Low, in which the initial discrimination was trained with an intermittent reinforcement schedule and a lower obtained reinforcer rate. In both conditions, reinforcers followed all correct responses during reversal training. Reversal learning error rates were higher in the High condition for 8 subjects. Thus, the rate of reinforcement during the initial discrimination training was related to the persistence of stimulus control, as shown by more selections of the initially positive stimulus during reversal training in the High condition. The results are consistent with behavioral momentum theory. The results indicate that (a) behavioral momentum may describe stimulus control in discrete-trial procedures, and (b) teaching procedures may sometimes benefit from tactical reductions in local reinforcement density to encourage changes or transfers of stimulus control.