Date of Award


Degree Name

Master of Arts



First Advisor

Dr. David O. Lyon

Second Advisor

Dr. Richard Malott

Third Advisor

Dr. Jack Michael

Access Setting

Masters Thesis-Open Access


Rats' lever pressing was studied in two experiments involving mixed schedules with equivalent interval and differential-reinforcementof- other-behavior components. It was observed that temporal stimuli controlled latency times when fixed temporal criteria were used, that this control weakened as temporal criteria were increased from 3 to 7 to 15 seconds, and that it was usually weak regarding interresponse times. The mean number of lever presses per trial was likely to increase in the process, although ulterior decreases were apparent for two of the seven subjects. When random temporal criteria (approximately averaging 8 seconds) replaced fixed ones, the response rate increased. Rapid changes in response rate were recorded when simple schedules were operational. These results were interpreted as contradicting Seligman's learned helplessness model of depression.