the Representativeness Heuristic

The representativeness heuristic is a mental shortcut where people judge the likelihood of something based on how much it resembles a typical example or stereotype. If an idea or person fits well with what we expect of a certain group or category, we often assume they belong or that the event is likely, even if other factors suggest otherwise. For example, assuming someone is a librarian because they are quiet and books-loving, even if statistical data shows most librarians are not like that. This heuristic saves mental effort but can lead to errors in judgment.