In a discrete-operant bar-press situation, four types of deprivation (food, water, water-plus-food, and no deprivation) were combined factorially with four levels of reward (0%, 4%, 1635, and 64% sucrose concentration). In acquisition, water (0% sucrose) served as an effective reinforcer only when Ss were deprived of water alone. Higher sucrose concentrations tended to produce correspondingly higher levels of performance when food, water-plus-food, and no deprivation were used. No such differences were obtained with water deprivation. Resistance to extinction was an increasing function of sucrose concentration when Ss were deprived of food and waterplus-food. No differences were observed under the other two deprivation conditions.
EXPERIMENTS WHICH HAVE EXAMINED THE PREFERENCE OF RATS in a choicesituation have shown that, regardless of the type of deprivation employed, rats tend to prefer higher concentrations of liquid sucrose. For example, Campbell (1958) andCollier, Vogel, Rega, and Young (1966) have demonstrated that the incentive value of sucrose is directly proportional to its concentration when Ss were food deprived, while Beck and Nash (1969) and Cohen and Tokieda (1972) have shown that the same relationship occurred with thirsty rats. In a non-choice situation there appears to be an interaction between the type of deprivation and level of sucrose. Under the conditions of food deprivation, acquisition and extinction performance have been shown to be an increasing function of sucrose concentration when possible confounding effects of satiation and consummatory variables have been controlled (Barnes & Tombaugh, 1970;Collier & Myers, 1961;McCloskey & Tombaugh, 1971). However, Beck (1963 reported that reinforced rates of responding tended to be the same across different concentrations of sucrose when water deprivation was used. Results from threshold studies further indicate that an interaction may exist between the effects of sucrose and type of deprivation employed. Food deprivation tends to lower the taste threshold while water depriva-