Linda and base rates
Told that Linda is 31, a philosophy major, and deeply concerned with social justice, most people rate "feminist bank teller" as more likely than "bank teller." But both conditions together can't be more probable than one—the conjunction fallacy. Likewise, we guess a shy, tidy man is a librarian and ignore the base rate that farmers vastly outnumber librarians.
The gambler's fallacy and the fix
After five heads in a row, people feel tails is "due," expecting even short sequences to look representative of 50/50. Stereotyping works the same way. The antidote is Bayesian thinking: start with base rates, then adjust for evidence. It's often studied alongside the availability heuristic and anchoring.
FAQ
- Are heuristics bad?
- No—they're usually fast and useful, but they produce predictable errors in some situations.
- Is the hot-hand fallacy related?
- Yes, though recent research suggests some streaks in basketball may be real.
Sources reviewed: 2026-10-26
References
- Kahneman, D., & Tversky, A. (1972). Subjective probability: A judgment of representativeness. Cognitive Psychology, 3(3), 430–454.
- Tversky, A., & Kahneman, D. (1974). Judgment under uncertainty: Heuristics and biases. Science, 185(4157), 1124–1131.
- Tversky, A., & Kahneman, D. (1983). Extensional versus intuitive reasoning: The conjunction fallacy in probability judgment. Psychological Review, 90(4), 293–315.