Influence of percentage-reinforcement on runway running of rats

Rats ran for continuous reinforcement (CR) in a runway for 160 trials prior to being trained for 176 trials with CR, or with one of three percentage reinforcement (PR) schedules: 75%, 50%, or 25%. All rats then were retrained with CR for 80 trials. Individual rat data showed a variety of relationships between asymptotic PR and CR speed in both the initial and final portions of the runway, and this variety was masked in the averaging of data across rats. The individual rat data were seen as consistent with suggestions that (1) a PR schedule allows for differential reinforcement of running speeds, so that final performance is determined by the specific speeds reinforced during training; and (2) a shift from CR to PR leads to an increase in running speed, if an increase is physically possible and the percentage of reinforcements is not too low. The data were not consistent with the account of asymptotic performance on PR and CR schedules that has evolved from frustration theory.