Wage rate, nonlabor income, and labor supply in rats

Abstract

Thirsty rats pressed a lever for water under fixed-ratio schedules, with or without free water at the start of the 1-hr session. Total water intake fell steadily as the fixed-ratio requirement increased; when the fixed-ratio requirements covered a relatively broad range, total lever presses rose and then fell as the requirement increased. Free water decreased total lever presses but increased total intake, especially at the higher fixed-ratio requirements; its effect on total intake proved relatively hard to detect, but grew more apparent as the amount of free water increased. The results conformed more closely to a recent revision of the conservation model than to the original model. By viewing milliliters per press as a wage rate, and free water as nonlabor income, results are brought to bear on predictions derived from economic labor supply theory. In economic terms, rising wage rates were accompanied by a rise followed by a fall in total labor supply, but a steady rise in total income, in conformity with the backward bending labor supply curve. Nonlabor income cut the supply of labor but raised total income, especially at the lower wage rates.