We are of two minds.

• Author: Kavanagh, Shayne
• Position: Thinking Fast and Slow - Book review

Thinking Fast and Slow

By Daniel Kahneman

Farrar, Straus, and Giroux

2011, 512 pages, $30

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Thinking Fast and Slow explores the differences between the two types of thinking we all engage in. System 1 could be described as "intuitive"; it works "automatically and quickly, with little or no sense of voluntary control" System 2 is more rational and "allocates attention to the effortful mental activities that demand it, including complex computations" System 2 provides a check against the impulsive character of System 1. Of course, a person is generally not aware of when they are using System 1 or System 2 thinking, but the distinction is important because, as Kahnmen points out, System 1 generally provides easier answers than complex problems demand and is prone to systematic biases. System 1 has little grounding in logic and statistics. It also can't be turned off. All of these features present challenges to complex problem solving and decision making.

To further complicate the issue, System 2 is lazy. To illustrate this point, Kahneman asks the reader to consider this question. 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. The correct answer is 5 cents. When this question was posed to students at leading universities, more than half gave the intuitive and incorrect answer, meaning that they failed to engage their System 2 to check System 1. The failure rate was more than 80 percent at less selective universities. The point is not necessarily that people who answer incorrectly aren't intelligent, but rather that they not engaged and are more willing to go with the first answer that comes to mind.

BIASES AND MENTAL ERRORS

After introducing System 1 and System 2, Thinking Fast and Slow describes a number of biases and mental errors that people are commonly subject to. Some of the most interesting are briefly described below.

Law of Small Numbers. Kahneman cites research findings that counties where the incidence of kidney cancer is lowest are mostly rural, sparsely populated, and located in traditionally Republican states in the Midwest, the South, and the West. What inferences might you draw from this information? Kahneman then tells us that the incidence of kidney cancers is also highest in counties that fit this same description. The reason for this apparent contradiction is the law of small numbers--these counties are sparsely...