Date of Award


Degree Name

Master of Arts



First Advisor

Dr. Alan D. Poling

Second Advisor

Dr. Galen Alessi

Third Advisor

Dr. R. Wayne Fuqua

Access Setting

Masters Thesis-Open Access


The present study was designed to examine the effects of gradual DPH withdrawal on the matching to sample performance of three mentally retarded persons. The percentage of correct responses per session served as the dependent variable and the sample and comparison stimuli were red, green, and blue illumination of translucent response windows. The results showed that doses of diphenylhydantoin considerably lower than the suggested optimim therapeutic level can impair the performance of mentally retarded individuals on a simple discrimination task. As doses were reduced for each subject, there were increases in the percentage of correct responding with the highest percentage correct being obtained after, and only after, the 0 mg dose was reached. The results are discussed in terms of generality, the matching to sample procedure being well suited to the study of drug effects with severely mentally retarded individuals, and implications for habilitation.