Lack of Effect of Prefeeding on Food-reinforced Temporal Response Differentiation and Progressive Ratio Responding

To investigate the effects of various prefeeding intervals on operant performance (time of partial satiation prior to assessment), adult male Sprague-Dawley rats were trained on two operant tasks: a temporal response differentiation (TRD) task thought to measure time discrimination and a progressive ratio (PR) task thought to measure motivation to work for food reinforcers. Endpoints included percent task completed, response rate, accuracy (TRD only) and breakpoint (PR only). During the two week baseline period, subjects were fed their daily allotment of food (9-12 g) 23 h prior to assessment. In subsequent weeks, subjects were partially satiated by prefeeding the daily allotment of food from 0.25 h to 6 h prior to operant assessment. Prefeeding had no significant effects on performance of either operant task. This study extends previous findings by demonstrating no effects of prefeeding interval on two dissimilar operant behaviors. Thus, the results do not support deprivation interval as a measure of hunger. A more accurate measure of hunger might be provided by the use of body weight or percentage thereof.