Demand Curves for Animal Consumers
实验表明非人类消费者的补偿性和普通需求曲线均向下倾斜，必需品为总互补品，非必需品为独立或总替代品，将价值理论概念扩展到非人类。
Results are reported from experiments showing that both income-compensated and ordinary (uncompensated) demand curves for nonhuman consumers are negatively sloped. Essential commodities are determined to be gross complements, while nonessential goods are independent or gross substitutes. The experiments extend the concepts underlying value theory to nonhumans and provide a basis for intensive experimental investigations of additional aspects of the theory.