Eating and drinking as a function of maintenance schedule

Abstract

Animals without water do not eat as much food as usual, and hungry animals do not drink much water (4, 8, 13, 16, 17, 20). Animals drink more after meals than at other times. The dog and hen (13) and the rat (20) show a drop in food intake during water deprivation. Dogs (5, 11) and rats (20) similarly drop in water intake during food deprivation. Rats drink more after a period of water deprivation during which food is available than after a similar period with no food available (17). The corresponding case for food intake apparently has not been investigated. After protracted periods of food or water deprivation, rats exceed in both drinking and eating their average value before deprivation (4). No systematic sets of data are available on these phenomena as they are encountered in studies of learning, although their signifigance for theoretical formulations of "motivation" and learning has not escaped some investigators (9, p.234; 22). Recent studies on "drive interaction," "drive discrimination," and on "cognitions" have involved the control of the behavior of food-deprived and of water-deprived rats by food and water placed in goal boxes and alleys (21). These have not had uniform results, so that it is pertinent to examine the matter more closely. Today's learning theorists are in fair agreement on a definition of "drive." This concept is an intervening variable, explicitly involving two sets of operations and implicitly a third.2 The first operations establish drives; e.g., for hunger and thirst, the animal is deprived of food and water, respectively, for a stated number of hours. The second class of operations is the measurement of classes of behavior (running, bar pressing, eating) that vary with the duration of the preceding deprivation. The third, implicit, operation is that of satiation, usually giving the animal access to food and water long enough so that it neither eats nor drinks for a specified period. "Satiation" operations vary considerably. In this experiment, the operations are depriving the animal of food or water, or both, through stated intervals of time following free feeding and free drinking. The measure of behavior chosen is the total weight, in grams, of food and water ingested by the animal in the first hour following the period of deprivation. The adequacy of these measures has been established by others (1, p.128; 2, 7, 15, 18, 19). The general plan of the experiment and the values of the variables investigated have been chosen to provide data useful for the interpretation of experimental data in the field of learning.