Abstract
In a series of three experiments, groups of food-deprived and water-deprived rats were given pairings of a retractable lever (CS(+)) with response-independent deliveries of either solid or liquid reinforcers. In Experiment 1 food-deprived rats given a solid-pellet reinforcer differentially tended to sniff, paw, mouth, and bite the CS(+) lever more often than a lever that was not paired with food (CS(-)), whereas food-deprived rats given a liquid reinforcer tended to differentially sniff, paw, and lick the CS(+) lever. 23(1/2)-hour water-deprived rats given liquid reinforcers showed very little CS(+) contact. In Experiment 2 increasing the severity of water deprivation from 23(1/2) to 47(1/2) hours significantly increased CS(+) contact. In Experiment 3, subjects that were simultaneously food and water deprived and given a water reinforcer failed to exhibit differential CS(+) contact, but subjects that were simultaneously food and water deprived and given a food reinforcer did acquire differential CS(+)-contact behavior. These results suggest that (a) even under a single motivational state the nature of signal-centered behavior can be determined by type of reinforcer, (b) although water reinforcement produces less signal contact than food reinforcement, this can be facilitated with more severe water-deprivation levels, and (c) high CS-contact rates using food reinforcement are not simply a product of reductions in body weight with food deprivation.