In the unlikely event of this book being made into a film, System 2 would be a supporting character who believes herself to be the hero.

(Chapter 2) System 2 is deliberate where System 1 is unthinking. Effortful where System 1 is easygoing. But System 1 is the true hero of Kahneman’s story, because for all its faults and quirks, System 1 does most of the work in our cognitive inner lives. It is constantly on duty, maintaining and updating our understanding of normality and flagging things that seem surprising, and making causal inferences to supply a running explanation of why the world around us behaves as it does.

David Freedman used to say that if the topic of regression comes up in a criminal or civil trial, the side that must explain regression to the jury will lose the case.

(Chapter 17) Kahneman is talking about regression to the mean. This statistical phenomenon is often mistaken for a causal one. Example: An investment analyst who has a spectacularly successful year picking winning stocks does less well the next year, while his colleague who performed poorly the year before does better. The causal explanation might be that the first analyst got complacent, while the second one applied herself better. The likely truth is that in the first year, one analyst was lucky and the other unlucky. The next year, both performances were more nearly average. Regression to the mean is a familiar concept for statisticians, but for lay people it is unintuitive. System 1 cannot grasp it; System 2 can be trained to grasp it (but not easily).

Once you adopt a new view of the world (or of any part of it), you immediately lose much of your ability to recall what you used to believe before your mind changed.

(Chapter 19) Kahneman is remarking on our habit of constantly revising our memories, especially our memories of things we used to believe and say that have turned out false. When a political contest ends or a verdict is returned in a highly publicized trial, people who made no prediction or made a false one will falsely remember having predicted the outcome correctly. The name for this trick of memory is hindsight bias. It is a major reason why people remain confident of their powers of foresight, even after experience ought to have taught them humility.

Professional golfers putt more accurately for par than for a birdie.

(Chapter 28) Here Kahneman combines two concepts from prospect theory, namely reference level and loss aversion. In the golf example, the reference level is par, the standard number of shots needed to finish a particular hole. A careful study showed that golfers putt with slightly greater accuracy when trying to avoid going over par (which relative to the reference level is a loss), than they do when trying to finish the hole under par (which relative to the reference level is a gain). The interpretation is that the golfers care more about making par (avoiding a loss) than going under it (achieving a gain). To emphasize that losses matter more than gains, Kahneman includes an observation made by psychologist Paul Rozin: A single cockroach will completely wreck the appeal of a bowl of cherries, but a cherry will do nothing at all for a bowl of cockroaches.

Odd as it may seem, I am my remembering self, and the experiencing self, who does my living, is like a stranger to me.

(Chapter 36) “The experiencing self” is Kahneman’s label for the perspective of experience in the moment. The remembering self is the perspective of memory, looking back. The two selves sometimes make very different assessments of the same events. Example: A diary kept by the experiencing self may record most days of a vacation as pleasant. But if the vacation ends on a sour note, for the remembering self this will cancel out the pleasure that came before. And the remembering self has the last word.

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