Peak-end Rule UP142

The peak–end rule is a psychological heuristic in which people judge an experience largely based on how they felt at its peak and at its end, rather than based on the total sum or average of every moment of the experience. The effect occurs regardless of whether the experience is pleasant or unpleasant. According to the heuristic, other information aside from that of the peak and end of the experience is not lost, but it is not used. This includes net pleasantness or unpleasantness and how long the experience lasted. The peak–end rule is thereby a specific form of the more general extension neglect and duration neglect.

The peak–end rule is an elaboration on the snapshot model of remembered utility proposed by Barbara Fredrickson and Daniel Kahneman. This model dictates that an event is not judged by the entirety of an experience, but by prototypical moments (or snapshots) as a result of the representativeness heuristic. The remembered value of snapshots dominates the actual value of an experience. Fredrickson and Kahneman theorized that these snapshots are actually the average of the most affectively intense moment of an experience and the feeling experienced at the end. The effects of the duration of an experience upon retrospective evaluation are extremely slight. Fredrickson and Kahneman labeled this phenomenon duration neglect. The peak–end rule is applicable only when an experience has definite beginning and end periods.

A 1993 study titled "When More Pain Is Preferred to Less: Adding a Better End" by Kahneman, Fredrickson, Charles Schreiber, and Donald Redelmeier provided groundbreaking evidence for the peak–end rule. Participants were subjected to two different versions of a single unpleasant experience. The first trial had subjects submerge a hand in 14 °C water for 60 seconds. The second trial had subjects submerge the other hand in 14 °C water for 60 seconds, but then keep their hand submerged for an additional 30 seconds, during which the temperature was raised to 15 °C. Subjects were then offered the option of which trial to repeat. Against the law of temporal monotonicity, subjects were more willing to repeat the second trial, despite prolonged exposure to uncomfortable temperatures. Kahneman et al. concluded that "subjects chose the long trial simply because they liked the memory of it better than the alternative (or disliked it less)."

While the peak-end rule in human eating behavior may not be as general as in other contexts, studies have discovered some contextual factors that are influenced by the rule. For example, the peak-end rule works for the evaluation of food when the price is low. Conversely, for expensive food, people tend to rely on their initial experience rather than the peak or end experience. A potential reason is that high-price payers form a higher expectation of the service than low-price payers do. If their high expectation initially deviates from the actual experience, the valuation on the overall service could be driven primarily by the beginning experience. Those paying low price may not have much expectation and therefore consider the peak to be much higher than high-price payers do. Thus, they are more likely to be influenced by the peak-end rule when evaluating the overall experience.

The theory is formed in a pizza study where people chose to pay $4 or $8 for their pizza buffet. For those paid $4, both the tastes of the last and the peak slices significantly predict the general evaluation for overall food taste. In contrast, for those paid $8, the first slice is more important in predicting the overall enjoyment. Therefore, in order to maximize customer satisfaction, higher-priced restaurants should put their best food in front of the consumer first. In a buffet setting, they could provide some signage to make more popular items salient or place the most popular foods first in the line. In lower-priced restaurants, serving tasty desserts at the end may increase customer's overall satisfaction.

The effect of the peak-end rule in eating behavior also depends on personal factors such as self-restraint level on food choice. Robinson et al. discovered that for unrestrained eaters key moments in eating experiences have a disproportionately large influence on remembered enjoyment of eating. However, restrained eaters’ judgements on food are not influenced by the peak or end of the recent eating experience but by other cognitive factors such as semantic knowledge and beliefs about food that are already formed.