This book details the results of the authors' research using laboratory animals to investigate individual choice theory in economics, particularly consumer-demand and labor-supply behavior and choice under uncertainty. The use of laboratory animals provides the opportunity to conduct controlled experiments involving precise and demanding tests of economic theory with rewards and punishments of real consequence. Economic models are compared with psychological and biological choice models along with the results of experiments testing between these competing explanations. Results of animal experiments are used to address questions of importance related to social policy. A number of new experimental results are reported along with summaries of the authors' previously published studies and related research.