What a Colonoscopy Study Says About Weeks That Blur Together

A trial published in 2003 by Donald Redelmeier, Joel Katz and Daniel Kahneman sounds like a joke. Half of 682 patients finishing a colonoscopy were randomly given a little extra time with the scope left in place, a stretch that was uncomfortable but milder than what came before. They had strictly more discomfort than the other half. Afterwards they rated the whole procedure as less unpleasant.

The peak-end rule is the finding that people judge a stretch of experience mainly by its most intense moment and its final moments, and give little weight to how long it lasted. That is why a gentle ending can improve a memory, and why a week with no peak and no ending worth noting leaves almost nothing behind. The Day Reconstruction Method was built to capture how a day felt before memory rewrites it.

What did the colonoscopy studies actually show?

Two papers matter, and they are often blurred together.

The first is Redelmeier and Kahneman (1996, Pain, vol. 66). They recorded pain minute by minute in 154 colonoscopy patients and 133 lithotripsy patients, then asked for a retrospective total. The recalled total tracked the worst moment and the last three minutes of the record. Length of the procedure did not make it be remembered as worse.

The second is Redelmeier, Katz and Kahneman (2003, Pain, vol. 104), the randomized trial above. The extended group rated the final moments as less painful, rated the whole experience as less unpleasant, and ranked it as less aversive among eight unpleasant experiences. Over a median 5.3 years of follow-up, about half of all patients came back for a repeat colonoscopy, and the extended group returned slightly more often.

The older cold-water experiment, by Kahneman, Fredrickson, Schreiber and Redelmeier in 1993, is covered in our explainer on the peak-end rule. The colonoscopy work matters here for a different reason: it is the case where someone deliberately engineered an ending and measured the result.

Why do ordinary weeks blur together?

A routine week has no peak to anchor on and no ending that differs from the middle. Monday’s commute resembles Thursday’s, and memory stores the pattern once instead of five times. Avni-Babad and Ritov (2003, Journal of Experimental Psychology: General) found that routine stretches were recalled as shorter than non-routine ones, a result unpacked in the holiday paradox post.

Combine the two ideas and you get a working picture, though not a tested one. Peak-end research was run on single episodes lasting minutes, and nobody has shown that it scales to a whole week of life. The extrapolation is plausible, and it is also an extrapolation.

Which ten minutes of a day carry the most weight?

If the rule holds loosely at larger scales, endings are the cheapest thing to change, because they are short and you control them. Three candidates:

• The last ten minutes of the evening. Ending the day on a phone scroll gives memory a flat, blurry final scene. A short walk, a call, or a few lines in a notebook gives it something with an edge. The Sunday version of this is covered in the Sunday night ritual.
• The last ten minutes of the workday. A closing note of what went well and what starts tomorrow turns a trailing-off ending into a marked one.
• The first ten minutes after waking. This is the opening, not the end, but it often colors the day’s first memory. Something small that you chose, such as sitting outside with a coffee before touching a screen, is enough.

None of these is a tested intervention. They are applications of an effect that Kahneman’s group measured in pain, and you can only check them against your own recall.

How many peaks does a week need?

There is no studied answer. The experiments each had one peak and one ending, so that is the unit the evidence supports.

A reasonable starting guess is one deliberate high point per week, plus one marked ending for each day. Pick the high point so that it differs from your routine on at least one axis: place, people, or difficulty. Then see on Friday what you can recall without checking a calendar. If the week still feels like one smear, add a second.

A friend-witnessed commitment is one way to make a weekly peak harder to skip. With an accountability app such as DontSnooze, a friend sees the proof that you got up, so a Saturday sunrise hike stops being a vague intention and becomes something someone else will notice. The app does not choose your peak for you, and nothing here shows that witnessed plans are remembered more vividly.

Can a good ending rescue a bad week?

Partly, and the evidence is on the pain side. The colonoscopy patients did not forget what happened. Their total memory shifted toward the milder finish. Treat the ending as a lever on how a week is summarized, not a way to erase what went wrong in the middle.

The practical takeaway is modest. Weeks feel full in memory when they contain at least one moment worth retelling and when they end on purpose, and both are cheap to arrange.

If the peak you want is new rather than merely good, self-expansion theory suggests choosing something unfamiliar and doing it with another person.

Researchers who compare happy, meaningful and varied lives call the last kind psychologically rich, and the evidence on how to add it is mixed but concrete.