Duration neglect is the psychological observation that people’s judgments of the unpleasantness of painful experiences depend very little on the duration of those experiences. Multiple experiments have found that these judgments tend to be affected by two factors: the peak (when the experience was the most painful) and how quickly the pain diminishes. If it diminishes more quickly, the experience is judged to be more painful. Hence the term “peak-end rule” describes this process of evaluation.
In one study Daniel Kahneman and Barbara Frederickson showed subjects pleasant or aversive film clips. When reviewing the clips mentally at a later time, subjects did not appear to take the length of the stimuli into account, only as if they were a series of affective “snap shots”.
In another demonstration, Kahneman and Frederickson with other collaborators had subjects place their hands in painfully cold water. Under one set of instructions, they had to keep their hand in the water for an additional 30 seconds as the water was slowly heated to a warmer but still uncomfortably cold level, and under another set of instructions they were to remove their hand immediately. Otherwise both experiences were the same. Most subjects chose to repeat the longer experience. Subjects apparently judged the experience according to the peak-end rule, in other words, according to its worst and final moments only, paying little attention to duration.