Excessive drinking in the rat: Superstition or thirst?

Abstract

Three tests were made to help choose between 2 expanations of Falk''s finding of excessive drinking in rats that bar press for food pellets on a variableinterval schedule. One explanation assumes that drinking is adventitiously reinforced by food; the other assumes that eating a dry pellet makes a rat thirsty and that the spaced character of feeding allows it to take a drink after each pellet. The following findings support the second explanation (a) drinking ceased immediately when a liquid rein-forcer (milk) was substituted for dry pellets; (b) licking by the water spout ceased when the reservoir was empty; (c) switching to a fixed-interval schedule made it evident that rats drink after, and not before, bar pressing and eating.