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What it argues
Irrationality is Stuart Sutherland's rigorous and often mordant survey of the ways human beings consistently fail to reason well. Published in 1992, before Daniel Kahneman's Thinking, Fast and Slow made cognitive bias a mainstream topic, the book drew on decades of experimental psychology to document the gap between how people think they make decisions and how they actually do. Sutherland, a professor of experimental psychology at the University of Sussex, wrote the book for general readers and brought to it both scholarly exactness and a dry wit that makes the failures of human reasoning feel both dismaying and occasionally comic.
The book covers a wide range of cognitive failures: the misuse of statistics (people persistently misunderstand base rates, conditional probability, and sample sizes), the influence of availability on judgment (we estimate the frequency of causes of death by how easily examples come to mind, not by how common they actually are), obedience to authority even when it produces clearly wrong outcomes, and the tendency to form and maintain beliefs on inadequate evidence. Sutherland documents each failure with experimental evidence, from Milgram's obedience studies to Kahneman and Tversky's work on heuristics and biases.
What it gets right
- 1.
Cognitive biases are not quirks. They are systematic, predictable failures of reasoning that persist even when people know about them and are trying to think carefully.
- 2.
People are very bad at using statistical information. Base rates, conditional probability, and sample sizes are routinely misunderstood even by trained professionals in their own domains.
- 3.
The availability heuristic causes people to judge frequency and probability by how easily examples come to mind, producing systematic distortions in perceived risk.
What it covers
Who wrote it
Stuart Sutherland (1927–1998) was a British experimental psychologist and professor at the University of Sussex, where he also served as director of the Centre for Research on Perception and Cognition. He was a co-founder of the journal Perception and the editor of the Macmillan Dictionary of Psychology. He published scientific papers on animal cognition, visual perception, and decision-making, and was known for combining rigorous scholarship with accessible prose. Irrationality, published in 1992, remains his most widely read work and anticipated by nearly a decade the mainstream popularization of cognitive bias research.
