What is a summary of Thinking, Fast and Slow?

Thinking, Fast and Slow is a non-fiction book published in 2011 by Daniel Kahneman, winner of the 2002 Nobel Prize in Economics. Kahneman is an Israeli-American psychologist interested in the psychology of decision making and behavioral economics. In this best-selling work, Kahneman attempts to popularize his research and make it accessible to a general public.

Classical and neo-classical economics base their models on a notion of what is sometimes called the "homo economicus" or "economic man." In other words, classical economists assume that we can create economic models based on the assumption that humans act in a rational and well-informed manner to promote their self-interest and economic well being. Kahneman and other behavioral economists argue that this assumption is false and that to understand economic behavior we must study how people act as individuals in the real world and use tools such as psychology to understand the basis for their actions. This will enable us to understand many economic and political phenomena inexplicable by classical economics, including those in which people act against their own actual self-interest.

In Thinking, Fast and Slow, Kahneman describes two different systems of thought, fast thinking (emotional, quick, automatic, subconscious) and slow thinking (logical, infrequent, careful, conscious). He argues that most of our decisions, such as steering a car on an empty road or not drinking spoiled milk because it smell disgusting, are made on the basis of fast instinctive thinking. Solving complex problems, such as parking in a small space or cooking from a complex recipe, require slow thinking. When applied to the same problem, these two types of thinking, according to Kahneman, may result in different solutions. 

Next, Kahneman discusses how these types of thinking use different methods of thought. He says that fast thinking involves assimilating new data or situations to known patterns, while slow thinking involves seeing new patterns. For example, a fast thinking approach to going vegetarian might mean substituting a "meatless" hamburger based on soy protein for a beef hamburger, while a slow thinking approach might include reading up on Indian and other vegetarian cuisines and learning what people in those cultures eat for lunch. 

Kahneman then examines in detail the various heuristic patterns, such as framing, avoidance, sunk-cost, availability, and substitution, that form the basis of how we make actual decisions, even when those decisions are inherently irrational. He concludes with a section on human happiness and how we judge our own happiness.