Thinking, Fast and Slow: Part 5, Chapter 35 Summary & Analysis

Kahneman provides two different definitions for utility: “experienced utility,” which refers to the enjoyability of outcomes as people live them, and “decision utility,” which refers to the desirability of a choice. He writes that these two concepts will coincide if people want what they enjoy and enjoy what they choose for themselves.

Kahneman creates a puzzle that asks whether people would pay more to reduce a number of planned injections from 20 to 18, or from 6 to 4. Usually, people would pay more to reduce the number from 6 to 4 because it reduces the proportion of injections. But this is somewhat nonsensical, because in each case a person is reducing the total pain by the same amount. The person pays different amounts to achieve the same gain of experienced utility.

Kahneman then examines the experience of two patients undergoing a painful colonoscopy. His study was conducted in the early 1990s, before anesthetics were widespread for the procedure. The patients were prompted every 60 seconds to indicate their pain level. A graph shows that Patient A’s procedure lasted 8 minutes and finished with the peak pain intensity the person experienced—8 on a scale of 10. Patient B’s procedure lasted 24 minutes and also had a peak pain intensity of 8, but the pain deescalated over the second half of the procedure.

Most people believe that Patient B had a more painful procedure because they had the same peak intensity as Patient A, but their procedure lasted longer. Surprisingly  Patient A rated their procedure as much more painful. This led to two findings: 1) The peak-end rule, which holds that the overall rating of the procedure is predicted by the level of pain reported at the worst moment and at the end. 2) The duration of the procedure has no effect. These findings have implications for medical practice: if the objective is to reduce patients’ memory of pain, lowering peak intensity and end intensity could be more important than minimizing the duration of the procedure.

It is difficult to distinguish the experiencing self (which answers the question “Does it hurt now?”) from the remembering self (which answers the question “How was it, on the whole?”). Kahneman reports how an audience member in a lecture of his stated that a record scratch at the end of a record ruined the experience, despite the fact that the past is fixed.

The remembering self has more decision-making power than the experiencing self. In an experiment, people are exposed to two experiences: first, 60 seconds of putting their hand in a cold-water bath; second, 60 seconds of putting their hand in a cold-water bath followed by thirty additional seconds with slightly less cold water. People prefer to repeat the second experience rather than the first, even though the second experience encompasses the first experience, because they have a less aversive memory of that experience due to the peak-end rule.

Kahneman describes how these rules have bases in biology: even rats ignore duration of pain and pleasure and only focus on the peak intensities of each emotion. This function of memory is a feature of System 1, and it is not necessarily rational.