Effects of water temperature on the reward value and satiating capacity of water in water-deprived rats

Abstract

Since orolingual cooling is a primary reward for water-deprived rats, cold water should be more rewarding than warm water. Hooded rats were allowed to bar press on a VI 1-min schedule for water at approximately 12° or 36°C. Testing started when their body weights had dropped to 80% of their predeprivation levels and was continued as their weights were allowed to drift slowly upward. Mean number of bar presses for cold and body-temperature water were compared under the various body-weight conditions, and in almost all cases the rats bar pressed at a higher rate for cold water. When these same animals were again deprived to 80% body weight, they showed an overwhelming preference for cold water over warm water in 10-min choice tests. A third experiment with these animals replicated Kapatos and Gold's (1972) finding that rats offered either only warm water or only cold water in different test sessions drink more warm water than cold. The results of these experiments are consistent with the hypothesis that cold water is both more rewarding and more satiating than is body-temperature water, but it could be that the intake of cold water is terminated prematurely by the drop in body temperature which it produces.