Divided stimulus control: Which key did you peck, or what color was it?

Responding on concurrent schedules produced a conditional discrimination (Phases 1 and 2), asking either which peck produced the event, or which color the keys were when the event was produced. In Phases 3 and 4, reinforcer delivery or a delay in blackout was interpolated between responding and the conditional discrimination. In Phase 1, location versus color discrimination accuracy was controlled by the relative reinforcer frequency for correct responses to these questions (divided stimulus control). In Phases 2 to 4, relative reinforcer frequency for correct responses to these questions was .5, and the relative frequency with which concurrent-schedule responses produced the questions was varied. This variation had no clear effect on the accuracy of reporting Location or Color. These results are consistent with the model of divided control suggested by Davison and Elliffe (2010). Arranging a 3-s reinforcer between responding and choice decreased both color and location accuracy, but a 3-s delay only decreased location accuracy. Thus, in concurrent-schedule performance, both ambient stimuli prior to a reinforcer and the location of the just-reinforced response are available as discriminative stimuli following the reinforcer. Control of postreinforcer responding is divided between these according to their association with the relative frequency of subsequent reinforcers.