Prospect Theory

One-Sentence Definition

People tend to be risk-averse when facing gains and risk-seeking when facing losses.

Core Concept

Kahneman and Tversky proposed that people’s risk preferences are not fixed—they become conservative when facing gains (certainty effect) and adventurous when facing losses (reflection effect). The value function is S-shaped.

What Problem Does It Solve

When information is incomplete, options are numerous, or risks are unclear, it helps pull your judgment from intuition back to structured analysis.

More specifically, Prospect Theory is suited for answering questions like: How can I better understand the current situation? How can I make more reasonable judgments and take action?

When to Use

• When problems become complex and intuitive judgment is no longer reliable.
• When the team has disagreements about next steps and needs a shared analytical framework.
• When you need to translate abstract judgments into concrete actions, checklists, or experiments.
• When existing practices are losing effectiveness and the underlying logic needs re-examination.

When Not to Use

• The problem is simple, and direct execution is more important than analysis.
• Basic facts are lacking, and you are just spinning concepts.
• The model is used only to confirm existing conclusions rather than to help correct judgment.

Summary

Prospect Theory explains many irrational economic behaviors and is a cornerstone of behavioral economics.