Date of Award


Degree Name

Doctor of Philosophy



First Advisor

Dr. Arthur Snapper

Second Advisor

Dr. David Lyon

Third Advisor

Dr. Bradley Huitema

Fourth Advisor

Dr. Dennis Simpson


A discrete-trial choice procedure was conducted in which pigeons were sequentially exposed to four constant variable-interval schedules against each of which five different fixed-interval schedules were compared. The five fixed-interval comparison values were presented in a descending then ascending sequence for the first three variableinterval standard conditions. The fixed-interval sequence was reversed for the last variable-interval standard condition. The variableinterval standard conditions were 10, 20, 40, and 40 seconds, respectively, and the five fixed-interval comparison steps for each variable-interval standard condition ranged from a maximum of twice the variable-interval standard to continuous reinforcement in five equal steps. There were 50 elements comprising each variable interval standard condition value for one group and 3 elements in each variable interval standard for the other group. Exclusive preference for both groups changed from the variable-interval standard condition value, at high fixed-interval comparison values, to the lowest fixedinterval comparison value when the fixed-interval comparison values were low. This effect was clearly demonstrated for all variableinterval standard conditions. Measures of response rate and latency in the four forced-choice trials (only one alternative available) that preceded each choice trial (both alternatives available) systematically varied with choice behavior for all subjects. Response rates in the variable-interval forced-choice trials were highest at large fixedinterval comparison values and lowest at the minimum fixed-interval comparison value. Response rates in fixed-interval forced choice trials were exactly opposite for the same fixed-interval comparison values. Latencies in the fixed-interval forced-choice trials were highest at the maximum fixed-interval comparison value and lowest at the minimum fixed-interval comparison value. Latencies for variableinterval forced-choice trials were exactly recersed for the same fixedinterval comparison values. Response distributions for each tenth of a forced-choice variable-interval standard value and fixed-interval comparison value showed equal distributions of responding for the variable-interval schedules and positively accelterated responding for the fixed-interval schedules.

The direct measure of relative and absolute choice with the discrete-trial procedure appears easier to use and understand than results obtained from concurrent-chains preference testing.

Access Setting

Dissertation-Open Access

Included in

Psychology Commons