Behavioral Finance

Behavioral finance studies how systematic departures from the rational-investor benchmark — biased beliefs, reference-dependent preferences, limits to arbitrage, and bounded cognitive capacity — shape asset prices, household decisions, and corporate-finance policy. The field is organized around three core pillars (irrational expectations, behavioral preferences, limited arbitrage) plus a fourth complementary set of bounded-rationality patterns, and tested against a stable set of empirical anomalies (excess volatility, return predictability, the equity premium, momentum, household-portfolio puzzles, dividend-policy persistence, sentiment-driven mergers). The course progresses from the empirical anomalies that motivate the field, through the cognitive and preference-based mechanisms proposed to explain them, to the asset-pricing applications (bubbles, momentum, reaction models), the household-level applications (non-participation, under-diversification, the disposition effect, under-annuitization, liabilities puzzles), the bounded-rationality and prescriptive-policy chapters, and the corporate-finance and dividend-policy applications. The course closes with the reaching-for-yield result on how the macroeconomic interest-rate environment shapes individual risk-taking.

The unifying claim is that the same small set of cognitive ingredients — overconfidence, extrapolation, representativeness, loss aversion, mental accounting, present bias, limited attention, categorical thinking — appears across the asset-pricing, household-finance, and corporate-finance branches. The branches are the same theory applied at different levels of aggregation and to different decision-makers (investors, households, managers).

Intuition

Neoclassical finance assumes rational agents in frictionless markets, which delivers the efficient-markets benchmark and the rational asset-pricing models. Behavioral finance keeps the equilibrium machinery but relaxes one or both of those assumptions: agents may form biased beliefs or hold non-standard preferences, and arbitrageurs may face binding trading constraints that prevent them from correcting mispricings. The result is a framework that can match the empirical anomalies the rational benchmark struggles with, while still making testable predictions about prices, volume, and individual choice.

The course is built around the contrast between the rational benchmark and its behavioral alternatives. Each anomaly is introduced first as a violation of the rational model, then as a target for behavioral explanation. The asset-pricing chapters (bubbles, noise, momentum, reaction models) focus on how mispricings arise and persist in equilibrium. The household-finance chapter shows the same biases driving individual portfolio choices that the rational life-cycle model cannot match.

Children

• 8.1. Principles of Behavioral Finance — the three pillars (limits to arbitrage, behavioral preferences, biased beliefs) and the critiques the field must answer.
• 8.2. Distribution of Prices — empirical facts about return distributions that any pricing model must match.
• 8.3. Challenges to Rational Pricing — the excess-volatility, predictability, and equity-premium puzzles that motivate behavioral finance.
• 8.4. Noise — Pillar 1: Limits to Arbitrage. Market noise, the no-trade theorem, and the DSSW noise-trader risk model.
• 8.5. Prospect Theory — Pillar 2: Behavioral Preferences. Kahneman-Tversky reference-dependent, loss-averse preferences and cumulative prospect theory.
• 8.6. Belief-Based Biases — Pillar 3: Biased Beliefs. Conservatism, representativeness, base-rate neglect, extrapolation, and experience effects.
• 8.7. Bubbles — first application. The rational-bubble impossibility results and the behavioral bubble models (Miller, Harrison-Kreps, Scheinkman-Xiong).
• 8.8. Momentum — the cross-sectional and time-series momentum anomalies, and why momentum crashes.
• 8.9. Reaction Models — over- and under-reaction frameworks (BSV, Hong-Stein) that explain momentum using belief-based biases.
• 8.10. Behavioral Household Finance — household portfolio puzzles (non-participation, under-diversification, disposition effect, under-annuitization, liabilities) driven by prospect theory and cognitive biases.
• 8.11. Bounded Rationality — Pillar 4 (complement to belief biases): bounded rationality. Limited attention, attention-grabbing stocks, the $1/n$ heuristic, nominal illusion, categorical thinking and excess comovement.
• 8.12. Prescriptive Behavioral Finance — policy-design companion to bounded rationality: financial literacy, financial advice / audit studies, nudges and default options, explicit de-biasing.
• 8.13. Behavioral Corporate Finance — corporate-finance application: market timing, catering, sentiment-driven investment and M&A, managerial over-optimism, overconfidence/miscalibration, single firm-wide discount rate.
• 8.14. Dividends — dividend-puzzle hub: DDM, clientele theory, life-cycle theory, behavioral theories (bird-in-hand, self-control, mental accounting), inertia-based theories.
• 8.15. Reaching for Yield — capstone application: low interest rates increase risk-taking through reference-dependence and salience mechanisms (Lian-Ma-Wang $2019$).

See Also

• 1. Finance — top-level Finance hub.
• 4. Portfolio Management — the rational portfolio-choice and asset-pricing benchmark this course departs from.
• 5. Corporate Finance — the rational corporate-finance benchmark that the behavioral-corporate-finance chapter departs from.