Thinking, Fast and Slow: Part 1, Chapter 3 Summary & Analysis

Kahneman relays that System 2 has a natural speed. We expend some mental energy in considering random thoughts and in monitoring what goes on around us, but normally there is little strain. We make many small decisions and absorb pieces of information without much effort.

Normally, it is easy to walk and think at the same time, but at the extremes these activities compete for resources. If we are asked while walking to compute 23 x 78, we will surely stop. Or if we walk at a very fast pace, we hinder our ability to think.

Often, we also have to monitor our self-control while we think. Maintaining difficult cognitive work requires effort not only in thinking, but in forcing ourselves to continue that work (like reading a difficult book). Sometimes, however, people are able to expend considerable effort for long periods of time without having to exert willpower, which psychologist Mihaly Csikszentmihalyi calls flow.

It has been proven that self-control and cognitive effort are both forms of mental work. People who are asked to retain seven digits for a minute or two and are simultaneously offered the choice between a fruit salad and chocolate cake are more likely to select the cake. When we are cognitively busy, we are less able to maintain self-control.

Psychologist Roy Baumeister discovered that if you have to force yourself to do something, you are less willing or less able to exert self-control when the next challenge presents itself, something called ego depletion. Or, if you successfully exert self-control in one task, you often do not feel like making an effort in another.

Baumeister’s group also showed that the idea of “mental energy” is not a metaphor. The nervous system consumes more glucose than most other parts of the body, and people who were given lemonade with sugar before participating in a focusing task did not show the same ego depletion that people who were given lemonade with Splenda.

A disturbing effect of ego depletion in judgment was recently reported. Judges in Israel spent days reviewing applications for parole. The judges were much more likely (65% approval vs. 35% approval) to approve requests at the beginning of the day and after a meal. When they are ego depleted, they fall back on the easier position of denying parole.

One of the main functions of System 2 is to monitor the actions “suggested” by System 1. Kahneman provides a sample puzzle: “A bat and ball cost $1.10. The bat costs one dollar more than the ball. How much does the ball cost?” The intuitive answer is 10 cents, but this is the wrong answer. More than 50% of the students at Harvard, MIT, and Princeton gave the incorrect answer. At less selective universities, the rate of failure was 85%.

These percentages are shocking, considering that checking the math would require only a few seconds of extra work. Failure to answer the bat-and-ball problem correctly, as well as other puzzles like it, is a matter of insufficient motivation. People who avoid the wrong answer are more alert, intellectually active, and more skeptical about their intuitions.

Researchers have spent some time trying to discover the connection between cognitive aptitude and self-control. In a famous experiment, Walter Mischel gave four-year-old children the choice between a small reward (one Oreo) which they could receive at any time, or a larger reward (two cookies) for which they could wait 15 minutes.

About half of the children manage to wait for the two cookies. Ten or fifteen years later, a large gap had opened up between those who could wait and those who could not. The resisters had high measures of self-control, were less likely to take drugs, and had substantially higher scores on intelligence tests.

This test shows that some people think more with System 1, and some think more with System 2. Keith Stanovich and Richard West, who introduced the terms System 1 and System 2, believe that intelligence is not the only thing that distinguishes these two kinds of people. Stanovich believes they are more rational—a quality he believes to be distinct from intelligence.