Behavioral finance as a subdiscipline of behavioral economics is finance incorporating findings from psychology and sociology into its theories. Behavioral finance models are usually developed to explain investor behavior or market anomalies when rational models provide no sufficient explanations. To understand the research agenda, methodology, and contributions, this survey reviews traditional finance theory first. Then, this survey shows how modifications (e.g. incorporating market frictions) can rationally explain observed individual or market behavior. In the second section, the survey will explain the behavioral finance research methodology -how biases are modeled, incorporated into traditional finance theories, and tested empirically ...