This study discusses the Behavioral Finance, one of the most important and controversial innovations in finance, that confronts the traditionally accepted paradigm based on the Modern Finance Theory. Initially, a synthesis of potential problems of decision-making is carried through, with examples of some non-rational aspects that make up important paradoxes in finance. After a discussion of the prospect theory, the seminal experiments of Kahneman and Tversky are replicated in a Brazilian sample. Many situations that violate premises of the theory of the expected utility, base of the Modern Finance Theory, are presented. Empirical results show that evidences of many perception biases in decisionmaking are consistent, independently of aspects related with the evolution of the market and the culture or nationality of individuals. The separation between theory and practice in financial decisions suggests the Behavioral Finance as an alternative to explain attitudes of economic agents.
Behavioral finance; investor behavior; modern finance theory; expected utility theory; cognitive biases