Peak-End Rule (Wikipedia)
An encyclopedia article on the peak-end rule: Kahneman and Fredrickson’s heuristic that people judge a past experience mainly by its most intense moment and how it ended, the key experiments establishing it (the cold-water study, colonoscopy studies), and its documented business, medical, and service applications. Wikipedia articles are continuously edited, so year above reflects the access date (2026-07-13), not a fixed publication year.
License: CC BY-SA 4.0 — https://creativecommons.org/licenses/by-sa/4.0/
Key points
- The rule is an elaboration of Kahneman and Fredrickson’s “snapshot model” of remembered utility: an experience is judged not by its total or average, but by the average of its most affectively intense moment (peak) and its final moment (end). The accompanying duration neglect effect means the length of an experience has only a slight effect on how it’s remembered.
- Founding evidence: a 1993 cold-water study (Kahneman, Fredrickson, Schreiber, Redelmeier) where subjects preferred to repeat a longer, objectively more painful trial because it ended less unpleasantly than the shorter one.
- 1996 and later colonoscopy/lithotripsy studies (Kahneman & Redelmeier; Kahneman, Redelmeier & Katz) found patients rated procedures as less unpleasant, and were more willing to return for future procedures, when a procedure ended with a period of reduced (not absent) discomfort — even when that made the procedure objectively longer.
- A boundary condition (Kahneman & Carmon): for waiting-line experiences, how a person felt at the very end predicted their retrospective evaluation even when much of the wait was dissatisfying — real-time expectations get discounted after the fact if unfulfilled.
- Two causes given for the effect: a memory bias toward more emotionally intense moments (people don’t correct for the fact remembered instances skew toward extremes), and ordinary recency bias (endings are easier to recall than earlier parts of a sequence).
- Documented applications: customer service (a strong ending — a held door, a free sample — can outweigh earlier friction, though the effect weakens for day-length-or-longer experiences like hotel stays); pricing strategy (reference price behaves as a weighted average of the highest and most recent price seen); a “streak-end rule” extension to sequences of good/bad events affecting worker turnover; vacation happiness recall; and medical-procedure comfort design.