Likelihood is judged by resemblance to a stereotype rather than by base rates.
Tversky and Kahneman's finding, and the Linda problem is the sharpest case. The heuristic is usually serviceable — resemblance often does track likelihood — and fails exactly where base rates are extreme.
In practice
- Told a man is shy and tidy, people judge him more likely a librarian than a farmer, ignoring that farmers vastly outnumber librarians.
- A recruiter shown a candidate who "looks like an engineer" weights the resemblance and not the base rate of who applies.
- Further reading
- Wikipedia
- Subject
- Decision-making & Reasoning
- Essay
- The catalogue of predictable errors