More rapid associative change with retraining than with initial training

Retraining was compared with initial acquisition in 4 magazine approach experiments with rats and 1 autoshaping experiment with pigeons. The levels of performance were matched prior to reinforcement and nonreinforcement for stimuli with a history of both training and extinction and stimuli with only a minimal history of training. Under these conditions, a previously extinguished stimulus was more vulnerable both to the incremental effects of reinforcement and to the decremental effects of nonreinforcement compared with a stimulus that had only been minimally trained.