Traditional finance or classic economics, portrays a person as a rational, self-interested individual who can maximise their utility, with full agency and information, able to discern the best course of action amongst their choices. In essence, a perfectly rational human being.
This has evolved to the current bastion neoclassical thought exemplified by the Chicago School[1], which is heavily influenced by rational expectations theory[2]. A classic example is Fama’s Efficient market Hypothesis[3], which postulates in securities markets prices are perfectly efficient and reflect all available information. This is predicated upon the assumption that individuals are always maximising their expected utility when making decisions.
Traditional finance took a one-dimensional approach, considering man as an island, when constructing their theories for the sake of convenience.
“Behavioral Economics is the combination of psychology and economics that investigates what happens in markets in which some of the agents display human limitations and complications.”[4]
As the economic profession developed, new theories were developed to supplement the one-dimensional assumption that individuals are pure utility maximizing agents. Many studies have shown that individuals are more likely to consider sub-optimal economic outcomes stemming from behavioural biases or risk mitigation purposes. Thus, the field of behavioural finance was developed to understand the human decision-making process in practice as opposed to a simplified theoretical version expounded by classical economics.
Behavioural finance is a multi-dimensional approach to analysing the true reaction function of agents on a macro and micro economic level in a better approximation of reality.
The best example between traditional finance and behavioural finance is the Ultimatum game. This is where one player is given a sum of money and proposes a split with the second player, the second player can accept the split or reject the split, if the second player rejects the split, then none of the players get anything, if the second players accept, both part ways with the split determined by the first player. Offers less than 30% to the second player are rejected 50% of the time[5].
A utility maximising individual should have chosen any outcome as their base case was nothing and any split is something. Results show that other issues come to fore, such as personal equity, when humans make decisions. While traditional finance does provide a simple guide to understanding human behaviour, it is too simplistic a model. Behavioural finance is a burgeoning field which seeks to better understand our decision matrix.
[1] University of Chicago
[2] John F. Muth (1961) “Rational Expectations and the Theory of Price Movements” reprinted in the new classical macroeconomics. Volume 1. (1992): 3–23 (International Library of Critical Writings in Economics, vol. 19. Aldershot, UK: Elgar.)
[3] Fama, Eugene F. “Efficient Capital Markets: A Review of Theory and Empirical Work.” The Journal of Finance 25, no. 2 (1970): 383–417. https://doi.org/10.2307/2325486.
[4] Mullainathan, Sendhil and Thaler, Richard H., Behavioral Economics (September 2000). Available at SSRN: https://ssrn.com/abstract=245828 or http://dx.doi.org/10.2139/ssrn.245828
[5] Güth, Werner; Schmittberger, Rolf; Schwarze, Bernd (1982). “An experimental analysis of ultimatum bargaining” (PDF). Journal of Economic Behavior & Organization. 3 (4): 367–388. doi:10.1016/0167-2681(82)90011-7