Timing compound stimuli: Relative reinforcer probabilities divide stimulus control in the multiple peak procedure.

Previous research suggests that when multiple stimuli signal the location of future reinforcers, the extent of control by each stimulus depends on the relative reinforcer probability associated with that stimulus. In this experiment, we asked whether relative reinforcer probabilities also divide control between stimuli that signal the time to future reinforcers. Six pigeons responded in a multiple peak procedure in which 2 dimensions of a compound stimulus-a color (red or green) and a frequency of on/off alternation (fast or slow)-signaled a fixed-interval 2- or 8-s schedule. Across conditions, we varied the probability of reinforcer deliveries associated with each dimension from .1 to .9. Relative reinforcer probabilities determined the degree of control by each stimulus dimension; as the probability of reinforcer deliveries associated with one dimension increased, a peak in response rates at the time signaled by that dimension became apparent while a peak at the time signaled by the other dimension diminished. However, these effects of relative reinforcers were smaller than in previous research, probably because elapsed time also competed for control over behavior. These findings extend the relation between relative reinforcers and divided stimulus control from spatial to temporal discriminations. (PsycInfo Database Record (c) 2020 APA, all rights reserved).