Rats were used in an experiment which investigated the effects of partial and continuous reinforcement of the CER. A 2 x 2 mixed design provided for the factorial combination of 100% and 50% reinforcement schedules with two discrete conditioned stimuli. Analysis of bar press suppression revealed a significant within-subjects reversed PRE. A numerical, but not significant reversed PRE was obtained in the between-subjects comparisons. Further, suppression in the presence of the tone CS was greater than that in the presence of the light CS. The results were discussed in terms of a fear conditioning model and a predictability model. / Master of Science