SPACED-TRIALS PARTIAL REINFORCEMENT EFFECT AS A FUNCTION OF CONTRAST

120 rats trained with consistent reinforcement in spaced trials show an inverse relation between resistance to extinction and amount of reward. However, with partial reinforcement, the relation is direct. There is a partial reinforcement effect (PRE) with large reward but not with small. 24 consistently reinforced rats show negative contrast in a Crespi experiment with shift to zero reward. 48 partially reinforced Ss show negative contrast when shifted to low reward. In massed trials, consistency and amount of reward interact as in spaced trials, although small rewards produce the PRE. Schedule of partial reinforcement has different effects on resistance to extinction in massed and spaced trials. These results suggest that different mechanisms produce the PRE in massed and spaced trials, and that the spaced-trials mechanism is contrast. (26 ref.) (PsycINFO Database Record (c) 2006 APA, all rights reserved). © 1969 American Psychological Association.