Divided control by past behavior, present stimuli, and future outcome value in a concurrent-chains procedure.

When multiple stimuli appear to signal behavior-reinforcer contingencies, control may be divided between those stimuli. Such divided stimulus control depends in part on the value of the outcome to the organism, with stimuli signaling more valuable outcomes exerting stronger control. The present experiment investigated how divided control by past and present stimuli interacts with outcome value. Pigeons responded in a concurrent-chains procedure in which one terminal link ended with two food deliveries after 8 s and the other link ended with six food deliveries after 48 s. Outcomes were signaled by the response producing terminal-link entry (past behavior) as well as keylight stimuli during initial links (past signals) and terminal links (present signals). When these sources of stimulus control conflicted, past behavior exerted strong control over terminal-link responding, overshadowing control by past signals. Some control by present signals was also evident, particularly at later times in terminal links. Additionally, stimuli signaling pigeons' more preferred outcome (smaller-sooner reinforcer) exerted stronger control than stimuli signaling the less preferred (larger-later) outcome. These findings highlight the importance of subjective outcome value in stimulus control and demonstrate that egocentric stimuli can exert enduring behavioral control even when other less transient discriminative stimuli occurred in the recent past or present.