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A particularly intriguing phenomenon pertains to sequences of stimuli, such as the sequences of painful experiences one might have to endure during an outpatient diagnostic procedure. Consider the following two sequences, where “1” signifies very low pain, and “10” signifies extremely intense pain. Suppose that you had experienced both sequences at different times. Now it was necessary to have one of the sequences repeated. Which sequence would you prefer to endure? Sequence A: 5, 6, 7, 10, 10, 10 Sequence
B: 5, 6, 7, 10, 10, 10, 9, 8, 7, 6, 5, 5, 5, 5, 5, 4, 3, 1 Because Sequence A lasts less than half as long as Sequence B and also because A is a subset of B, one would assume that people would prefer to experience A again rather than B. However Redelmeier and Kahneman (1996) have shown that this assumption may be in error. They asked patients undergoing either colonoscopy or lithotripsy to provide real-time ratings of the pain they were experiencing. Patients also provided retrospective judgments of how painful the procedures were. Redelmeier and Kahneman found that the remembered judgments of total pain were strongly correlated with the peak intensity of the pain and the pain experienced during the last few minutes of the procedure. The duration of the pain did not significantly influence the magnitude of the remembered pain. Therefore Sequence A, which has a high peak intensity and a very painful ending, would be remembered as more painful than Sequence B, which has a high peak intensity but a far less painful ending. Because duration does not influence the recollection of the total intensity of the pain, Sequence B’s longer exposure does not result in high retrospective evaluations of pain. If the “peak and end” of a sequence determine its recollected painfulness, then patients’ experiences can be manipulated in a counter-intuitive fashion. For example, if a dentist is concerned that a patient may not return for a second necessary but painful procedure, would it be ethical for the dentist to lengthen the initial procedure by adding some mildly painful moments? The recollected pain would thereby lessened, and the return visit would be more likely to occur. On the other hand, “Do no harm” would seem to imply that unnecessary pain should be avoided. Note that if less pain is in one’s own best interests, then patients should always prefer Sequence A. Evidence suggests that they do not (Kahneman, Fredrickson, Schreiber, and Redelmeier, 1993)
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