Abstract
Study objective: The present experiments investigated the effects of absolute reinforcer amounts, weight level, and economic conditions on rats' choices between 2 alternatives differing in reinforcer amount. In Experiments 1 and 3, a relatively smaller supplemental food was provided after each session (open-economy condition) and a shorter session time was used (closed-economy condition) to maintain weight at about 80% of free-feeding weights, while in Experiment 2, a relatively larger supplemental food and longer session time were used to maintain weight at about 95% of free-feeding weights. A demand curve analysis was applied to the relation between food consumption and responding, in addition to an analysis of preference. Rats' preferences differed only between a 1:3-pellet and a 4:12-pellet condition. The slope of demand functions obtained was steeper in the open-economy condition than in the closed-economy condition, irrespective of the difference in weight. These results indicate that the slopes of demand functions are determined by differences in economic conditions, either open or closed economies, as defined, for rats, by the absence or presence of supplemental food.
