Date of Award


Degree Name

Doctor of Philosophy



First Advisor

Dr. Jack Michael

Second Advisor

Dr. Alan Poling

Third Advisor

Dr. R. Wayne Fuqua


This study tested the following hypotheses: (a) The preference reversal phenomenon will be found when the delays to reinforcement are defined by fixed-ratio schedules, (b) The preference reversal phenomenon will be observed when intra-delay reinforcers are programmed, and (c) Imposing response requirements during the delay to reinforcement will affect preference for a larger delayed reinforcer over a smaller more immediate reinforcer. In Experiment 1, pigeons chose between two schedules, each a sequence of two fixed-ratio schedules. The second schedule of one sequence offered a small reinforcer and the second schedule of the alternative offered a larger reinforcer. The latter sequence always required more responses than the former. The initial fixed-ratio schedules, which were always equal, programmed access to grain or a hopper flash. The results showed that preference shifted from the sequence with the smaller reinforcer to the sequence with the larger reinforcer (i.e., preference reversal) as the size of the initial fixed-ratio increased. Whether food or a hopper flash followed the initial fixed-ratio did not greatly affect this relation. When the duration of the hopper flash was increased in other conditions, responding for the sequence with the larger reinforcer increased. These results showed the preference reversal phenomenon when the delays to reinforcement were defined by fixed-ratio schedules and when intra-delay reinforcers were programmed. Thus, the phenomenon is not restricted to procedures in which single time-based schedules define the delays. In Experiment 2, pigeons chose between two fixed-ratio schedules or two fixed-time schedules. One schedule of each pair programmed 2-s access to grain; the other, 8-s access to grain. Preference for the schedule with the 8-s reinforcer decreased in some conditions when subjects moved from a choice between the fixed-ratios to a choice between the fixed-time schedules. These results suggest that preference for a larger more delayed reinforcer is dependent on the type of schedule used to define the delays to reinforcement.

Access Setting

Dissertation-Open Access