Thinking, Fast and Slow · chapter 10 · id thinking-fast-and-slow-c10-02-people-neglect-base-rates-when

“People neglect base rates when making probability judgments, relying instead on representativeness -- as shown in the lawyer-engineer problem.”

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Receipts

Kahneman & Tversky (1973), Psychological Review 80(4)DOI registry: valid

Participants' probability estimates were driven primarily by personality descriptions (representativeness) and barely influenced by base rates (70/30 vs 30/70 split), even though base rates should have large Bayesian impact.

Gigerenzer & Hoffrage (1995), Psychological Review 102(4)DOI registry: valid

When base rate problems are presented in natural frequency formats rather than probability formats, performance improves from ~15-20% correct to 45-50%+. The 'bias' partly reflects format incompatibility, not deep irrationality.

Cosmides & Tooby (1996), Cognition 58FLAGGED: DOI not in registry

Humans perform much better on base rate problems when information is presented as natural frequencies rather than single-event probabilities, consistent with evolutionary adaptation to frequency-format information.

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