Peak-End Rule | Kaelan

Daniel Kahneman had patients undergo two versions of an uncomfortable medical procedure. Version A: moderately painful for 8 minutes. Version B: moderately painful for 8 minutes, then slightly less painful for 7 more minutes. Version B is objectively worse — more total pain. But patients remembered B more favorably. The ending was less bad, and memory judges by endings.

This is the peak-end rule: our retrospective evaluation of an experience is the average of its most intense moment and its final moment. Duration barely matters. A vacation with three great days and one miserable last day is remembered worse than three okay days and one great last day — even if the first had more total pleasure.

The rule separates the experiencing self from the remembering self. The experiencing self cares about moment-to-moment sensation, duration included. The remembering self writes the story and makes future decisions — and the remembering self uses peaks and endings, not integrals. The two selves want different things from the same experience.

This creates exploitable patterns. Doctors can improve remembered experiences by managing endings, not totals. Service businesses can earn loyalty with strong finishes. Storytellers know to end well. What happens last overwrites much of what came before in the ledger of memory.

The dark side: the rule can mislead. A bad relationship with occasional peaks and a tender ending is remembered fondly despite mostly being painful. A good project with a rough conclusion is remembered as a failure despite mostly succeeding. Memory is not justice; it’s a heuristic that can be gamed.

The practical wisdom: knowing that endings disproportionately shape memory, design experiences with the ending in mind. And when evaluating past experiences, ask what your remembering self might be distorting. The story you tell about what happened is not what happened.