Date of Award


Degree Name

Doctor of Philosophy



First Advisor

Dr. Howard Farris

Second Advisor

Dr. Alan Poling

Third Advisor

Dr. Galen Alessi

Fourth Advisor

Dr. Abraham Nicolaou


Three severely mentally retarded adolescents were studied under discrete-trial procedures in which a choice was arranged between edible reinforcers that differed in magnitude and, in some conditions, delay. In the absence of delays, the larger reinforcer was consistently chosen. All subjects directed the majority of choice responses to the smaller reinforcer when the larger reinforcer was sufficiently delayed, although the value at which this occurred differed across subjects. Under conditions where the larger reinforcer initially was sufficiently delayed to result in preference for the smaller one, progressively increasing in 5-s increments the delay to both reinforcers increased percent trials with the larger reinforcer chosen. At sufficiently long delays, two of the subjects consistently chose the larger but more delayed reinforcer and the third subject chose that reinforcer on half of the trials. These results are generally consistent with the findings of prior studies in which adult humans responded to terminate noise and pigeons re-responded to produce food.

Access Setting

Dissertation-Open Access