Date Available


Year of Publication


Degree Name

Master of Science (MS)

Document Type

Master's Thesis


Arts and Sciences



First Advisor

Dr. Thomas Zentall


In the successive delay-discounting task, all trials start with a stimulus to which a response results in a small amount of reinforcement (smaller-sooner). If no response is made, the stimulus changes and a response results in a larger reinforcer (larger-later). The purpose of this study was to examine the use of a non-reinforced distractor (a stimulus to which responding has no programmed consequence) as a method of increasing the proportion of larger-later (LL) choices in a successive delay-discounting task. Earlier research studying the use of distractors may have inadvertently associated the distractor with reinforcement. Four experiments were conducted and each focused on a different aspect of the procedure: prior reinforced training with the distractor, increased experience with the delay-discounting task, inclusion of a constant delay between choice and reinforcement, and the presence of a response-dependent LL stimulus, respectively. Contrary to what has been found in previous studies, the results from the first 3 experiments suggest that there is little evidence that pigeons will use a non-reinforced distractor in order to obtain a greater amount of reinforcement, while the fourth found a significant distractor effect. Further research is necessary to examine the efficacy of a distractor in a successive delay-discounting task.

Digital Object Identifier (DOI)