── ── Mental model
Peak-End Rule
People remember experiences not by averaging all moments but by sampling two: the peak (highest emotional intensity) and the end. Everything in between — including duration — is largely discarded. This is the peak-end rule, from Kahneman et al. (1993) and Redelmeier & Kahneman (1996).
Run Peak-End Rule on a real problem
Bring something you're actually deciding — free, in the browser.
How it works
Run the Peak-End Audit. Emotion map first, then peak and ending diagnosis, then redesign.
Stop-rule: If you cannot map the experience into a temporal sequence of stages with varying emotional intensity, the peak-end rule does not apply.
1. Map the experience timeline. List every significant stage in chronological order. Estimate emotional intensity (-5 to +5) per stage. Note where intensity spikes, dips, and what the emotional state is at the last touchpoint. 2. Identify the current peak. Highest intensity stage — positive or negative. Document: is it designed or accidental? Positive or negative? Strategically placed? 3. Identify the current ending. Emotional state at the last touchpoint. Flag if it is neutral/procedural (checkout confirmation, invoice, exit survey). 4. Diagnose the gaps. Peak gap: strong enough and positive? Ending gap: warm and memorable? Negative peak risk: any negative stage overwhelming the positive peak? 5. Design the peak intervention. One moment exceeding expectation significantly. Intensity correlates with surprise gap (actual minus expected), not absolute quality. Specify: what moment, what "exceeding expectation" means, estimated cost vs. expected lift. 6. Design the ending intervention. Highest-ROI optimization. Principles: (a) make the person feel remembered; (b) leave a tangible memory artifact; (c) point forward, not backward.
When to use it
- user says 'how will they remember this,' 'experience design,' 'journey design,' 'memorable moment,' 'end-of-experience,' or 'our NPS is lower than expected'
- when designing or auditing a multi-stage customer or user journey
- when a competitor with similar quality earns higher recommendation rates
When not to use it
When the decision is routine and reversible, applying a formal method costs more than it returns.
Worked example
Redelmeier and Kahneman — Colonoscopy Study (1996)
A primary-source-documented clinical case; not a business parable.
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