Effects of preshift small magnitude of reward received during goalbox placements on the negative contrast effect

During preshift, one experimental group of rats was given a large magnitude of food reward following a traversal of a straight alley and during a goalbox placement, while the other experimental group was given a small reward during goalbox placement and a large reward following a run. During postshift, all experimental groups were given a small reward of food following a traversal down the runway and during a goalbox placement. A control group was maintained on small reward during placements and following a traversal throughout the study. Only the group who received preshift large reward during placement and following a runway response ran slower to small reward during postshift than the control group maintained on small reward (negative contrast effect).     

Perseveration of the partial reinforcement effect in extinction with rats over two phases of extinction and two stages of continuous reinforcement

One group of 10 male albino rats was given partial reinforcement while the other 10 rats received continuous reinforcement in a straight alley. Subjects then experienced five consecutive stages of Extinction 1, Continuous Reinforcement 1, Extinction 2, Continuous Reinforcement 2, and finally, Extinction 3. Analysis showed the partial reinforcement effect in extinction was sustained over two stages of extinction and two stages of continuous reinforcement, since subjects receiving partial reinforcement ran faster than rats given continuous reinforcement throughout all three of the extinction periods. The results seem to support those of Amsel's (1967) and Cabpaldi's (1967) theoretical formulations of the partial reinforcement effect in extinction.