Expected Utility Theory vs. Behavioral Alternatives
Behavioral economics challenges traditional economic assumptions by incorporating psychological insights into decision-making. This module explores Expected Utility Theory (EUT), a foundational concept, and its limitations, leading into key behavioral alternatives that better explain real-world choices.
Expected Utility Theory (EUT)
Expected Utility Theory, pioneered by John von Neumann and Oskar Morgenstern, provides a normative framework for rational decision-making under uncertainty. It posits that individuals choose among gambles to maximize their expected utility, which is the weighted average of the utilities of possible outcomes, with weights being the probabilities of those outcomes.
EUT assumes rational choices maximize expected utility.
EUT models decisions as choosing the option with the highest expected value of utility. This means people are rational, consistent, and make choices that are logically sound.
The core of EUT lies in the concept of utility, which represents an individual's subjective satisfaction or value derived from an outcome. For a gamble with outcomes and corresponding probabilities , the expected utility is calculated as . A rational decision-maker, according to EUT, will always choose the gamble that yields the highest expected utility. This theory is built upon a set of axioms, including completeness, transitivity, independence, and continuity, which define rational preferences.
Individuals make choices to maximize their expected utility.
Limitations of Expected Utility Theory
Despite its elegance, EUT has been shown to be descriptively inadequate, meaning it often fails to predict how people actually behave in real-world situations. Empirical evidence from various studies has revealed systematic deviations from EUT predictions.
EUT is a 'normative' theory (how people should decide), but behavioral alternatives are 'descriptive' (how people actually decide).
The Allais Paradox, first presented by Maurice Allais, highlights a violation of the independence axiom of EUT. Consider two choices:
Choice 1: A gamble offering 5 million with 10% probability, 0 with 1% probability.
Most people choose Choice 1. Now consider a second set of choices:
Choice 3: A gamble offering 0 with 89% probability. Choice 4: A gamble offering 0 with 90% probability.
Most people choose Choice 4. However, if EUT holds, choosing Choice 1 over Choice 2 implies that the utility of 1 million from both gambles (which is what the independence axiom suggests should happen) should lead to choosing Choice 3 over Choice 4. The fact that people often reverse their preference demonstrates a violation of the independence axiom.
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Another significant challenge comes from prospect theory, developed by Kahneman and Tversky. Prospect theory addresses several empirical regularities not captured by EUT, such as loss aversion and the way people perceive probabilities.
Behavioral Alternatives to EUT
Several theories have been proposed to provide more accurate descriptive models of decision-making under uncertainty.
Prospect Theory
Prospect theory describes how individuals evaluate potential losses and gains. Key features include:
- Value Function: People evaluate outcomes relative to a reference point (often the status quo), and the disutility of a loss is generally greater than the utility of an equivalent gain (loss aversion).
- Probability Weighting: People tend to overweight small probabilities and underweight moderate to high probabilities. This is known as probability distortion.
A value function (incorporating loss aversion) and probability weighting.
Cumulative Prospect Theory (CPT)
An extension of prospect theory, CPT addresses some of the technical issues of the original formulation, particularly regarding the treatment of probabilities and the independence axiom. It uses cumulative probabilities, which resolves some paradoxes and provides a more robust descriptive model.
Other Behavioral Models
Other models, such as regret theory and disappointment theory, also attempt to capture psychological factors influencing decisions under uncertainty, focusing on the emotional consequences of outcomes.
Feature | Expected Utility Theory (EUT) | Prospect Theory (PT) |
---|---|---|
Decision Basis | Maximizing expected utility of final wealth | Evaluating gains and losses relative to a reference point |
Risk Attitude | Can be risk-averse, risk-neutral, or risk-seeking based on utility function | Risk-averse for gains, risk-seeking for losses; exhibits loss aversion |
Probability Handling | Uses objective probabilities | Uses subjective probability weighting (overweights small, underweights large) |
Key Axiom Violated by Behavior | Independence Axiom (e.g., Allais Paradox) | N/A (descriptive model) |
Empirical Testing and Experimental Design
The distinction between normative EUT and descriptive behavioral theories is often tested through carefully designed experiments. These experiments present subjects with choices involving gambles and analyze their decisions to see if they align with EUT or exhibit patterns predicted by behavioral models.
Key Experimental Paradigms
Common experimental designs include:
- Choice Tasks: Presenting subjects with pairs of gambles and asking them to choose.
- Preference Reversal Tasks: Designing scenarios where EUT predicts consistent preferences, but behavioral biases might lead to reversals.
- Field Experiments: Conducting experiments in real-world settings to test the applicability of these theories outside the laboratory.
Presenting subjects with choices between different gambles.
Conclusion
While Expected Utility Theory provides a powerful normative benchmark for rational decision-making, behavioral alternatives like Prospect Theory offer more accurate descriptive accounts of how individuals actually make choices under uncertainty. Understanding these differences is crucial for developing more realistic economic models and effective policy interventions.
Learning Resources
Provides a comprehensive overview of Expected Utility Theory, its axioms, and historical development.
The seminal paper introducing Prospect Theory, detailing its core concepts and empirical evidence.
An accessible introduction to behavioral economics, covering its key ideas and contrast with traditional economics.
Explains the Allais Paradox and its implications for the validity of Expected Utility Theory.
A video lecture introducing the field of behavioral economics and its foundational concepts.
Details Cumulative Prospect Theory, an extension of Prospect Theory that addresses some of its limitations.
Daniel Kahneman's Nobel lecture, discussing his work on prospect theory and behavioral economics.
Lecture notes on microeconomic theory, including behavioral economics and experimental design principles.
A documentary segment on the life and work of Amos Tversky, a key figure in behavioral economics.
A more advanced paper discussing the theoretical underpinnings and analytical foundations of behavioral economics.