Cognitive biases
The peak–end rule: why we remember an event by its most intense moment and its ending
One summer, Emma went out of town with friends twice: once to a lake and once to a river. Both trips were good. Now her friends ask: “Which one should we repeat this weekend?” Emma stops to think: what does she actually remember about those days?
This is the peak–end rule: we judge a past event mostly by two moments, the most intense one and the last one. How long it lasted has almost no effect on the judgment. So when we decide whether to repeat a trip, a party, or a conversation, we rely not on the whole day but on its most vivid moment and its finale.
Below, we look at what research has shown, how far the rule can be trusted, and where it gets in the way in relationships and at work. In the middle of the article you will watch Emma’s two trips hour by hour and choose for yourself which one to repeat.
Contents
In short: how the peak–end rule works
What the peak–end rule is
The “peak” is the most intense moment of an event. In an unpleasant event it is the hardest moment, in a pleasant one the happiest. The “end” is the last few minutes. The rule says that these two moments do the most to decide how the whole event will be remembered.
The rule was described by the psychologists Barbara Fredrickson and Daniel Kahneman. In a 1993 paper, people watched pleasant and unpleasant video clips of different lengths and then rated each one as a whole. The length of a clip barely changed the rating. The scientists called this duration neglect: when we remember, the length of an event seems not to be counted.
The rule was also tested outside the lab. The researcher Donald Redelmeier, together with Kahneman, asked patients to report how much it hurt right during two unpleasant medical procedures. Later the patients rated how much pain there had been in total. Their ratings depended strongly on the most painful moment and on the last three minutes. Long procedures were not remembered as especially hard.
How far the rule can be trusted. In a large 2022 review of studies, the rule got strong support: the peak and the end are closely linked to how people later rate the whole event. Duration had almost no effect. But there is an important caveat: a simple average over all moments predicted the rating about as well. So memory does not throw away the middle; it just gives more weight to the peak and the end. And in a study with a real vacation, students reported every day how good they felt. The length of the trip did not affect the final rating, but the peak–end rule did not turn out especially accurate either. It seems that memory rebuilds long events in a more complicated way than it handles short lab experiments.
Try it yourself: Emma’s two trips
The game takes a couple of minutes. Here is what will happen.
Step 1. You will watch both of Emma’s trips hour by hour. Which one is shown first is decided by chance for each player.
Step 2. You will choose which trip you would repeat if it were your weekend.
Step 3. We will show both trips in full. Then you can change the last hour of the river trip yourself and see what happens.
Why are the trips shown one hour at a time? That way you go through the day in order, as Emma did, rather than looking at it from above. And the order is random, so that neither trip is “fresher” than the other for all players.
What usually happens. The best-known experiment was run in 1993 by Kahneman, Fredrickson, and their colleagues. The paper is titled “When More Pain Is Preferred to Less.” Participants held a hand in cold water, 14 °C, for a whole minute. That hurts. Another time they did the same with the other hand: the same minute at 14 °C, and then another half minute while the water was slowly warmed to 15 °C. It still hurt, but noticeably less. Then people were asked which of the two experiences they were willing to repeat. Most chose the long one. That is, more pain, but with a gentler ending.
Something similar was found with pleasant events. In experiments by the psychologist Ed Diener and colleagues, people read short descriptions of other people’s lives. A wonderful life that ended suddenly was rated higher than the same life with a few more merely pleasant years added. Even though the second one had more good in it. It is the same with Emma’s trips: the river had everything the lake had, plus another pleasant hour, but its ending turned out duller.
What the game can and cannot show. You did not live through these trips; you watched them from the side and could count every hour. In the cold-water experiment, people felt everything themselves. So your choice is a hint, not a test. But the game does show how the simplified “best moment plus end” formula works: as you move the last hour, you will see that in it the rating changes more than the total joy does. This is a model, not a measurement of real memory.
When it is not a mistake. Wanting good things to end well is normal. Leaving a party on a high note is a sensible choice. It becomes a mistake when, because of one bad ending, we decide that everything was bad and turn down something that mostly suited us.
Why memory counts this way
Imagine that memory keeps not a movie but a small album with a few photographs. The most vivid moment will surely get in. So will the last frame: it is the closest. But how many hours passed between the shots, you cannot tell from the album. This is an image, not the exact way memory works. But Fredrickson and Kahneman described something similar: the judgment of the past is built from a few “snapshots” of what was lived, as if duration did not matter.
Why the peak and the end are the easiest to see is not fully clear. In a 2000 review, Fredrickson writes that the rule is reliably confirmed, but with caveats. She suggests that the moments that mean the most to the person personally have the strongest influence on the rating.
Where it gets in the way
Relationships. A warm evening that ended in an argument at the door is remembered the next day as “we fought again.” Three good hours seem to vanish. This is an everyday observation, not a result of an experiment, but it follows directly from the rule. It works the other way too: a warm goodbye can soften the memory of a hard conversation. A bad ending also hits harder than a good one: that is what the negativity bias is about.
Work. A long project is later judged by its most frantic day and by how the handoff went. A meeting that ended with an awkward pause seems like a failure as a whole. And when we decide whether to take on similar work again, we rely on exactly this memory.
Vacations. A trip is often remembered by one vivid day and the ride home. The good ordinary days in the middle fade, though there were the most of them.
Medicine. In a 2003 study, half of the patients, chosen by lot, had an unpleasant procedure briefly extended so that the last minutes were less painful. These patients rated the procedure overall as less unpleasant and later came back for a repeat examination slightly more often.
How to use the rule
The peak–end rule is one of the biases on the cognitive bias map, in the section on memory. Also there is hindsight bias: how knowing the outcome rewrites what we thought before.
Frequently asked questions
So does duration not matter at all?
For how an event will be remembered, it hardly matters. For how you live through it, of course it matters. An hour of pain is an hour of pain, even if it later fades from memory. That is why scientists ask separately how a person felt in the moment and how they rate it all afterward.
Is this the same as hindsight bias?
No. Hindsight bias is about knowing the outcome: “I knew it all along.” The peak–end rule is about how the lived experience seems to us, good or bad, and whether we want to repeat it.
Is it wrong to want things to end on a good note?
No. Wanting good things to end well is normal, and leaving a party on a high note is a sensible choice. The mistake begins when, because of one bad ending, we decide that everything was bad and turn down something that mostly suited us.
