Resistance to extinction of a runway response in rats was determined after discrimination training and after continuous reward training. Small and large amounts of training were given under 2 discrimination conditions, with either 0% or 50% reinforcement to the negative stimulus (S-); the positive stimulus (S+) always received 100% reinforcement. Small amounts of any type of discrimination training produced generalized partial reinforcement effects, resistance to extinction being greater than after continuous reinforcement. After large amounts of training, increased resistance disappeared for Ss on simple discrimination, but persisted for Ss partially reinforced to S-. Results support either Logan's rg hypothesis or Lawrence and Festinger's dissonance theory. (PsycINFO Database Record (c) 2006 APA, all rights reserved)