Bank Heuristic Homicide Teller Feminist Linda Representativeness Events

This rule of thumb leans heavily on judgments of similarity. Events are judged as more likely if they’re similar to the prototype of the event than if they’re less similar. The heuristic is undoubtedly helpful more often than not. Homicide is a more representative cause of death than is asthma or suicide, so homicides seem more likely causes than asthma or suicide. Homicide is indeed a more likely cause of death than asthma, but there are twice as many suicide deaths in the United States in a given year than homicide deaths.

A particularly unnerving example of how the representativeness heuristic can produce errors concerns one “Linda.” “Linda is 31 years old, single, outspoken, and very bright. She majored in philosophy. As a student, she was deeply concerned with issues of discrimination and social justice and also participated in antinuclear demonstrations.” After reading this little description, people were asked to rank eight possible futures for Linda.  Two of these were “bank teller” and “bank teller and active in the feminist movement.” Most people said that Linda was more likely to be a bank teller active in the feminist movement than just a bank teller. “Feminist bank teller” is more similar to the description of Linda than “bank teller” is. But of course this is a logical error. The conjunction of two events can’t be more likely than just one event by itself. Bank tellers include feminists, Republicans, and vegetarians. But the description of Linda is more nearly representative of a feminist bank teller than of a bank teller, so the conjunction error gets made.