02 - Attention and Effort

Описание: Kahneman explains that System 2 functions with a limited resource: attention. When you're tired or multitasking, control diminishes and System 1 takes command. The chapter connects mental effort with performance, self-control, and errors: thinking "well" costs energy and we don't always invest it.

The chapter describes research showing that mental effort is measurable through physiological indicators like pupil dilation. When people engage in cognitively demanding tasks—such as holding several digits in memory while performing other operations—their pupils dilate. The harder the task, the more the pupils dilate, up to a point. When the task becomes too difficult and people give up, the pupils contract.

This research reveals that System 2 has limited capacity. If you are required to do several things at once, or to do one thing while preparing another, performance suffers. You cannot compute 17 × 24 while making a left turn into dense traffic, and you should not try. Unlike the parallel operations of System 1, System 2 operates serially—one task at a time. When System 2 is engaged, other System 2 activities are suppressed.

The chapter introduces the concept of "ego depletion"—the idea that exerting self-control is tiring. If you have resisted the temptation to eat chocolate, you are subsequently less willing to resist other temptations. Activities that require self-control are effortful, and the effort depletes the resource that is needed for other System 2 activities. This has practical implications: people who are cognitively busy are more likely to make selfish choices, use sexist language, and make superficial judgments in social situations.

An important finding is that mental effort and physical effort draw on a shared reservoir of glucose. Depleting glucose weakens self-control. This explains why difficult cognitive tasks and resisting temptations both feel effortful and why both are impaired by glucose depletion. The practical lesson: thinking hard makes you tired, and being tired makes you think less effectively.