Peak-End Rule

One-Sentence Definition

People’s evaluation of an experience depends on the peak moment and the feeling at the end, rather than the overall average.

Core Concept

Kahneman’s research found that when people evaluate an experience, they primarily focus on two moments—the moment of strongest emotion (the peak) and the feeling at the end of the experience (the end).

What Problem Does It Solve

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

More specifically, the Peak-End Rule 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 disagrees on the next steps and needs a shared analytical framework.
• When you need to turn 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 missing, and you are only spinning concepts in the air.
• The model is used only to confirm existing conclusions, rather than to help correct judgment.

Summary

When designing products and services, pay special attention to the quality of the peak experience and the ending experience.