Date of Award


Degree Name

Doctor of Philosophy



First Advisor

Dr. Arthur Snapper

Second Advisor

Dr. Jack Michael

Third Advisor

Dr. David Lyon

Fourth Advisor

Dr. Dennis Simpson


A discrete-trial choice procedure, in which pigeons were exposed to one constant and one variable duration of reinforcement, was used to assess the effects of session-by-session manipulations in the variable reinforcement duration on the choice behavior of the subjects. Two groups of pigeons were used. Each subject in the first group was exposed to the same constant reinforcement duration (1.5, 3.0 or 6.0 sec), but different fixed-ratio trial completion requirements (5, 15 and 45). The subjects in the second group were exposed to all three different constant reinforcement durations while the trial completion requirement was kept constant with a variable-interval 15 sec schedule of reinforcement.

Choice reversal was obtained on a reliable basis only during the variable-interval trial completion, 1.5 and 3.0 sec constant reinforcement conditions. Choice reversal also occurred with the fixed-ratio trial completion requirement but was dependent upon an interaction between the size of the ratio and the constant reinforcement duration.

Initial response latencies and running rates were a direct function of manipulations in variable reinforcement duration during the variable-interval trial completion conditions.

Although some data were obtained on which an analysis of amount of reinforcement in terms of "just reinforcing differences" could have been based, such was not done, given a number of confounding variables still present in the procedure.

It was concluded that the discrete-trial procedure could function as a viable alternative to other procedures which in the past have served to assess preference in non-human subjects.

Access Setting

Dissertation-Open Access