Behavioral economics and its related area of study, behavioral finance, use social, cognitive and emotional factors in understanding the economic decisions of individuals and institutions performing economic functions, including consumers, borrowers and investors, and their effects on market prices, returns and the resource allocation. The fields are primarily concerned with the bounds of rationality of economic agents. Behavioral models typically integrate insights from psychology with neo-classical economic theory. In so doing they implicate a range of concepts, methods, and fields. Behavioral analysts are not only concerned with the effects of market decisions but also with public choice, which describes another source of economic decisions with related biases towards promoting self-interest.During the classical period, microeconomics was closely linked to psychology. For example, Adam Smith wrote The Theory of Moral Sentiments, which proposed psychological explanations of individual behavior and Jeremy Bentham wrote extensively on the psychological underpinnings of utility. However, during the development of neo-classical economics economists sought to reshape the discipline as a natural science, deducing economic behavior from assumptions about the nature of economic agents. They developed the concept of homo economicus, whose psychology was fundamentally rational. This led to unintended and unforeseen errors.However, many important neo-classical economists employed more sophisticated psychological explanations, including Francis Edgeworth, Vilfredo Pareto, Irving Fisher and John Maynard Keynes. Economic psychology emerged in the 20th century in the works of Gabriel Tarde,George Katona and Laszlo Garai. Expected utility and discounted utility models began to gain acceptance, generating testable hypotheses about decision making given uncertainty and intertemporal consumption respectively. Observed and repeatable anomalies eventually challenged those hypotheses, and further steps were taken by the Nobel prizewinner Maurice Allais.