Experiential Amnesia: The Peak-End Rule

15.12.2017 |

Episode #8 of the course How cognitive biases are messing up your decisions by Abasi Latcham


We’re going to shift away from decision making for today and discuss memories and colonoscopies. First, though, let me introduce the peak-end rule.


What Is It?

The peak-end rule is a memory heuristic; that is, it’s a shortcut your brain uses to remember events. It means that our memories of positive or negative experiences depend on two things: the experience’s most extreme point (i.e. the peak) and its end (i.e. the end). We don’t remember the average level of happiness or discomfort, and time doesn’t really factor into it (this is called duration neglect). We evaluate our memories on peaks and ends.

What does this look like in practice? According to Kahneman’s TedX talk, he looked at patients undergoing colonoscopies in order to see. The simple version is that a patient’s memory of total pain was most strongly influenced by the worst pain during the procedure, and the pain felt right at the end. This meant that if there were two patients who each experienced the same levels of intense pain for the first three minutes, then Patient A’s treatment finished, while Patient B’s continued for another five minutes but at a lesser intensity, Patient A would remember the experience as being worse despite Patient A enduring less pain than Patient B.

Kahneman explains this effect by evoking a dichotomy of self; that is, we are both an experiencing self and a remembering self. The experiencing self lives for about three seconds at a time, on repeat, 500 million times throughout our lives, experiencing and (mostly) forgetting. By contrast, the remembering self “is relatively stable and permanent” and does its best to keep track of all our experiences in a coherent story. And what are the key points of a story? The climax and the ending. It is the conflict between what the experiencing self experiences and what the remembering self remembers that gives rise to the peak-end rule.

Another thought experiment: Suppose you have been at a concert, enjoying the show. However, just before the end of the set, some lunatic sets up an air horn to the speaker system and blasts the audience (you don’t go deaf but it sucks). You might say that this “ruined the whole experience.” But to quote Kahneman and Riis, “the experience was not ruined, only the memory of it”—the experiencing self thoroughly enjoyed the concert and the lunatic’s actions did not “remove” this enjoyment. “The confusion of experience with memory that makes us believe a past experience can be ruined is a compelling cognitive illusion. The remembering self is sometimes simply wrong.”



Here is an example of a painful and a pleasurable instance of the peak-end rule.

Childbirth: I’m not a woman, so I can’t speak from experience, but studies show that the peak-end rule is a good predictor of how labor pain is remembered. That is, the memories are more strongly influenced by the peak and final instances of pain, not the duration of labor.

Vacation memories: While your experiencing self has a clear bias for a longer vacation, your remembering self doesn’t seem too fussed. Studies show that the duration of a vacation doesn’t really impact on the recollection of the vacation, and that the “peak-end rule predicts approximately the correct level of happiness.”



There is no agreement on why we prefer to remember peaks and ends. However, because we know that we do, we can “hack” our memories for the benefit of our remembering selves. The simplest way to do this is to try to make sure your experiences end well. Plan the fun activity for the end of the trip. Leave the party before it dies. Don’t overeat dessert so that you feel sick. Do something cool on Sunday afternoon (or at least, don’t leave your chores until then).

Tomorrow, we will cover decision fatigue and discuss parole, clothes, and food.


Recommended reading

Evaluation by Moments: Past and Future


Recommended video

The Riddle of Experience vs. Memory


Recommended book

Thinking, Fast and Slow by Daniel Kahneman


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