BODY-WEIGHT AND RESPONSE AQUISITION WITH DELAYED REINFORCEMENT

The relation between body weight and responding established with unsig naled delayed reinforcement was investigated. In three experiments, na ive rats were deprived to either 70%, 80%, or 90% of ad libitum weight and were then exposed to tandem variable-interval 15-s differential-r einforcement-of-other-behavior 30-s schedules. The tandem schedule def ined a resetting unsignaled delay-of-reinforcement procedure. In the f irst experiment, speed of magazine training, acquisition of lever pres sing, and final rate of lever pressing were related to body weight. In the next experiment, lever pressing was established and maintained in rats that were magazine trained at 70% of ad libitum weight but that were then exposed to the delay procedure at 90% of ad libitum weight. Responding did not change consistently either across or within subject s in subsequent conditions in which body weight was manipulated. In th e final experiment, lever pressing was established and maintained with delayed reinforcement in the absence of magazine training for each of 2 rats at 70% and for 1 of 2 rats at 90% of ad libitum weight. The re sults further illuminate the conditions under which responding can be established in the absence of training and when such responses are rei nforced only following an unsignaled delay period.