Representativeness Heuristic

The representativeness heuristic judges category membership by how well something matches the typical image of the category, ignoring base rates.

Librarian or salesperson?

Someone is quiet, organized, and likes books. You assume librarian, even though salespeople vastly outnumber librarians. The librarian “feels” representative, so you skip the base rate.

One of Kahneman’s core heuristics, alongside Availability Heuristic and Anchoring.