Behavioral Economics
Behavioural economics is a field that combines insights from psychology with economic analysis to explain how people actually make decisions, in contrast to the assumption of fully rational, self-interested behaviour that underlies standard economic models. It identifies systematic patterns in judgement and choice, including biases, heuristics, and departures from consistency, and it examines their implications for markets, for policy, and for the design of institutions. The field has grown rapidly and has influenced both academic research and practical policy.
Departures from standard assumptions
Standard economic models assume that individuals have stable preferences, that they process information correctly, and that they maximise their own well-being. Behavioural economics documents systematic departures from these assumptions. People are often subject to framing effects, in which choices depend on how options are presented, and to anchoring, in which judgements are influenced by irrelevant starting points. They are overconfident about their knowledge and their abilities, and they are influenced by the behaviour of others.
These patterns are not random errors but systematic features of human cognition, arising from the ways in which people process information and make judgements. The recognition of these patterns has led to a richer understanding of behaviour and to models that incorporate the psychology of decision making, including prospect theory, which describes how people evaluate gains and losses relative to a reference point.
Prospect theory and loss aversion
Prospect theory, developed by Daniel Kahneman and Amos Tversky, is one of the central contributions of behavioural economics to the understanding of choice under risk. According to the theory, people evaluate outcomes relative to a reference point, such as their current situation, and they are more sensitive to losses than to equivalent gains, a phenomenon known as loss aversion. They also tend to overweight small probabilities and to underweight moderate and high ones.
The theory explains a range of behaviours that standard models struggle to account for, including the reluctance to realise losses, the tendency to hold losing investments too long, and the patterns of choice observed in laboratory experiments. It has implications for finance, for insurance, and for the design of contracts and incentives, and it is one of the most influential theories in the social sciences.
Heuristics and biases
Behavioural economics has identified a wide range of heuristics, or rules of thumb, that people use to make decisions, and the biases to which they give rise. Availability, in which judgements are influenced by how easily examples come to mind, and representativeness, in which probabilities are judged by similarity to stereotypes, are among the most studied. These heuristics are often useful, but they can lead to systematic errors in specific contexts.
The recognition of these patterns has implications for policy and for the design of markets. Defaults, in which an option is selected unless the individual chooses otherwise, have large effects on behaviour, because people tend to accept the default. Framing and the presentation of information influence choices, and the design of these elements can improve outcomes. These insights are the basis for the field of behavioural public policy, sometimes called nudging.
Applications
Behavioural economics is applied across many areas, including personal finance, where it explains patterns of saving and borrowing and informs the design of pension systems and of financial products; labour markets, where it informs the analysis of wage setting and of effort; and public policy, where it informs the design of taxes, benefits, and regulations. The design of default options, of disclosure, and of incentives draws on behavioural findings.
The field has also influenced the analysis of markets. It helps to explain anomalies in asset pricing, patterns of trading, and the behaviour of investors, complementing standard models of market efficiency. It informs the design of markets and of institutions, including the structure of auctions and the regulation of consumer finance, and it has become an integral part of modern economics.
Foundational Experiments and Anomalies
Behavioral economics grew from a series of experimental findings that contradicted the predictions of the rational agent model. The ultimatum game showed that responders reject offers they regard as unfair even when rejection leaves them worse off. Framing effects demonstrated that choices depend on how options are described, violating the principle of description invariance. Anchoring showed that arbitrary numbers can influence subsequent estimates.
Prospect theory provided a unified account of many of these anomalies by proposing that people evaluate outcomes relative to a reference point, are loss averse, and apply diminishing sensitivity so that the difference between small gains and small losses weighs more heavily than equivalent differences farther from the reference point.
Applications in Finance
Behavioral finance applies these ideas to asset markets. Limits to arbitrage explain why mispricing can persist when rational investors face risk, capital constraints, or horizons shorter than the time needed to correct the deviation. Overconfidence and representativeness can generate excessive trading and momentum. Disposition effects lead investors to sell winners too early and hold losers too long. These patterns matter for market efficiency debates and for the design of disclosure and default rules.
Applications in Public Policy
Behavioural insights have reshaped public policy through the use of defaults, framing, and reminders. Automatic enrolment in pension schemes, simplified forms, and timely prompts raise participation in savings and health programmes without restricting choice. This approach, sometimes called libertarian paternalism, seeks to improve decisions while preserving freedom. Critics question its ethical basis and whether measured effects persist over time.
Methodological Debates
The field relies heavily on laboratory and field experiments, complemented by observational data. Debates concern external validity, the replicability of classic findings, and the interpretation of heterogeneity. Some economists argue that apparent anomalies reflect rational responses to unobserved constraints or learning, while others hold that a richer model of cognition is needed. The productive tension has led to a substantial body of evidence and to refinement of both rational and behavioural models.