When: The Scientific Secrets of Perfect Timing

by Daniel H. Pink

You might have heard of the “peak-end rule.” Formulated in the early 1990s by Daniel Kahneman and colleagues including Don Redelmeier and Barbara Fredrickson, who studied patient experiences during colonoscopies and other unpleasant experiences, the rule says that when we remember an event we assign the greatest weight to its most intense moment (the peak) and how it culminates (the end).16 So a shorter colonoscopy in which the final moments are painful is remembered as being worse than a longer colonoscopy that happens to end less unpleasantly even if the latter procedure delivers substantially more total pain.17 We downplay how long an episode lasts—Kahneman calls it “duration neglect”—and magnify what happens at the end.