Effects of Trial Length and Delay of Reinforcement on Choice Behavior

Abstract

This study investigated the effects of varying trial length and delay of reinforcement on choice behavior. In Experiment 1 with pigeons as subjects, trial length was progressively lengthened while delay of reinforcement was kept constant, or delay of reinforcement was lengthened while trial length was kept constant. In Experiment 2 with rats as subjects, delay of reinforcement was kept constant while trial length was varied in successive conditions. Globally, with the pigeons, it was found that to lengthen the trial favored increments of choices of the larger delayed reinforcement; however, this finding was inconsistent between subjects; by contrast, varying delay of reinforcement resulted in clear decrements of the number of obtained reinforcers. A clear effect of varying trial lengths on the number of delayed reinforcers was found with rats. These findings confirmed the effect of varying trial lengths on choice behavior, as reported in previous literature. The importance of these findings for studies on self-controlled behavior and reversions of preference with humans and animals was discussed.