Representativeness Heuristic
Etymology
Coined by psychologists Daniel Kahneman and Amos Tversky in the early 1970s. "Heuristic" comes from Greek "heuriskein" (to find, discover) — the same root behind Archimedes’ cry of "Eureka." The term marks a rule of thumb that finds an answer fast but not always accurately.
noun phrase · /rep-rih-ZEN-tuh-tiv-ness hyoo-RIS-tik/
The mental shortcut of judging how likely something is by how closely it fits a stereotype.
What it names
Why we misjudge probability — mistaking resemblance to a prototype for the actual odds.
Example
Assuming the quiet, bookish man is a librarian rather than a salesman is the representativeness heuristic at work — there are far more salesmen.
Related idea
The representativeness heuristic judges by similarity; the base-rate fallacy is its usual consequence — ignoring how common each option actually is.