Representativeness heuristic
The representativeness heuristic is judging the probability of something by how closely it matches a mental prototype, rather than by actual statistics. If someone "looks like" a category, we assume they belong to it — ignoring how common that category really is.
Why it happens
The mind substitutes an easy question ("how similar is this to my stereotype?") for a hard one ("how probable is this?"). Similarity feels like evidence, so a vivid match overrides base rates, sample sizes, and randomness — the statistical facts that should actually drive the judgement.
Examples
- Told someone is quiet and loves books, guessing "librarian" over "salesperson" — though salespeople vastly outnumber librarians.
- Believing a coin sequence H-T-H-T-H is "more random" than H-H-H-H-H, though both are equally likely.
- Assuming a well-dressed, confident stranger must be successful and competent.
How to counter it
- Always ask for the base rate first: "How common is this category to begin with?"
- Treat similarity to a stereotype as a weak clue, not as a probability.
- Beware the conjunction trap — a detailed, "representative" story is less likely than its simpler version, not more.
The deeper point
It is the bias behind most stereotyping and most bad statistics at once: the same shortcut that makes a person "fit the profile" makes a gambler think a coin is "due." Similarity feels like evidence, but it is almost never probability.
Frequently asked
- What is the representativeness heuristic?
- It is judging how likely something is by how well it matches a stereotype or prototype, instead of by real statistics — so a vivid resemblance overrides how common the category actually is.
- What is an example of the representativeness heuristic?
- Hearing a shy, detail-loving description and guessing "librarian" over "farmer" — even though farmers are far more numerous, so the base rate makes farmer the likelier answer.
- How is it related to base-rate neglect?
- They are two sides of one error: judging by stereotype-match (representativeness) causes you to ignore how common the category is (base-rate neglect). Similarity crowds out frequency.
Related
Editorial synthesis © ReadGlobe 2026, drawing on Kahneman’s Thinking, Fast and Slow, the Tversky–Kahneman research program, and the primary cognitive-science literature. · Last reviewed 2026-05-29.