Topographical Differences Between Schedule-Induced and Prandial Drinking by Rats

Abstract

In Experiment 1 four white rats were exposed to a training regime in which water was available in one bottle when every bar press was reinforced and in another bottle when bar presses were intermittently reinforced. The animals learned to go to the bottle associated with the reinforcement schedule about 80% of the time and they drank more frequently, more regularly, and at a slightly faster tempo under the intermittent (schedule-induced drinking) than under the continuous reinforcement schedule (prandial drinking). In general this result was replicated in two further experiments with the same animals in which they could drink either from the bottle associated with the training schedule of Experiment 1 or from the one associated with the alternative schedule. The animals mostly drank from the bottle associated with the schedule in Experiment 1 and with the tempo and drinking pattern (response topography) that occurred with that bottle in that experiment. These results imply that schedule-induced drinking is in a different response class from prandial drinking. The two classes may be operant and elicited licks comparable to operant (response-reinforcement) and elicited (stimulus-reinforcement) key pecks or they may be two classes of operants under different discriminative and reinforcing stimulus control. In either event total water intake alone under a particular reinforcement schedule does not reveal the stimuli controlling drinking, and it may generate a misleading function relating schedule-induced drinking to environmental variables.