The influence of outcome delay on suboptimal choice

Under certain conditions pigeons will choose an option that provides less probable food over one that provides more probable food. This suboptimal choice behavior occurs when the outcomes are delayed and stimuli during the delay differentially signal the upcoming outcomes on the suboptimal alternative, but not the optimal alternative. The present study assessed whether duration of the outcome delay affects pigeons' suboptimal preference. Pigeons chose between a suboptimal alternative that provided food 20% of the time and an optimal alternative that provided food 80% of the time. Stimuli presented during the delays signaled the outcomes on the suboptimal alternative, but not on the optimal alternative. The outcome delays were 5 s in some conditions and 20 s in others. The results of two experiments demonstrate that behavior is generally more suboptimal when the outcome delays are longer but tends to stay relatively suboptimal if subjects experience the long delay condition before the short delay condition. The finding that behavior is more suboptimal with longer delays to the outcomes is consistent with the view that pigeons' suboptimal choice is influenced by both conditioned and primary reinforcement and is inconsistent with the view that suboptimal choice is influenced solely by signal value.