CHOICE BETWEEN SINGLE AND MULTIPLE REINFORCERS IN CONCURRENT‐CHAINS SCHEDULES

Pigeons responded on concurrent‐chains schedules with equal variable‐interval schedules as initial links. One terminal link delivered a single reinforcer after a fixed delay, and the other terminal link delivered either three or five reinforcers, each preceded by a fixed delay. Some conditions included a postreinforcer delay after the single reinforcer to equate the total durations of the two terminal links, but other conditions did not include such a postreinforcer delay. With short initial links, preference for the single‐reinforcer alternative decreased when a postreinforcer delay was present, but with long initial links, the postreinforcer delays had no significant effect on preference. In conditions with a postreinforcer delay, preference for the single‐reinforcer alternative frequently switched from above 50% to below 50% as the initial links were lengthened. This pattern of results was consistent with delay‐reduction theory (Squires & Fantino, 1971), but not with the contextual‐choice model (Grace, 1994) or the hyperbolic value‐added model (Mazur, 2001) as they have usually been applied. However, the hyperbolic value‐added model could account for the results if its calculations were expanded to include reinforcers delivered in later terminal links. The implications of these findings for models of concurrent‐chains performance are discussed.