Acquisition of instrumental responding following noncontingent reinforcement: Failure to observe 'learned laziness' in rats

Two experiments examined the possibility that presenting hungry rats with noncontingent food would interfere with the acquisition of instrumental responding for food reward. In Experiment 1 groups of rats received 0, 1, 10, or 20 50-min sessions, during which Noyes pellets were presented noncontingently on a variable time (VT) 60-sec schedule, and were subsequently trained to barpress for food reward. All three groups that received noncontingent food acquired instrumental responding for food reward more rapidly than the 0-session controls, but there was no indication that 10 or 20 sessions of exposure to noncontingent food produced slower acquisition of the instrumental response than 1 session. In Experiment 2 two groups were exposed to 1 or 30 1-h sessions, with food delivered on a VT 60-sec schedule. A third group lived 24 h/day in operant chambers for 15 days; food was delivered noncontingently on a VT 6-min schedule throughout the day. The latter group was then given a single 1-h session in the test chamber with food delivered noncontingently on a VT 60-sec schedule. During tests of instrumental responding for food, all three groups acquired the barpress response at similar rates. The present experiments fail to confirm earlier reports that prior exposure to noncontingent food impairs subsequent acquisition of food-rewarded responding by rats.