代表性ヒューリスティック

The representativeness heuristic is a mental shortcut where you judge the likelihood of something by comparing its similarity to an existing mental prototype—your idea of the most typical example of a group. For instance, you might assume someone is a yoga instructor based on their calm demeanor and healthy lifestyle because these traits match your mental image of a yoga teacher.

The representativeness heuristic causes errors because it ignores base-rate likelihood—the actual frequency of a category in the population. For example, assuming a fashionable woman reading about wine is a Master Sommelier overlooks that far more women work as janitors than hold that rare title, making the judgment statistically unlikely despite the apparent resemblance.

Stereotyping is a form of representativeness heuristic where you unintentionally categorize someone based on how well they match your mental image of a group. For example, assuming professors spend free time reading books and having intellectual conversations rather than playing volleyball reflects how closely their behavior aligns with your prototype of what professors should be like.

Yes, the representativeness heuristic can be valid when group members' traits actually cluster around the mental prototype. For example, in a town filled with yogis, assuming someone resembling a yoga instructor is indeed a yoga teacher may be accurate because most members share those characteristic traits.

Representativeness operates in cause-and-effect judgments through the principle that like goes with like. Astrology exemplifies this: the belief that birth signs influence personality assumes resemblance between a sign's characteristics and personality traits. However, research shows this relationship is invalid, demonstrating that apparent similarity does not establish actual causation.

A mental prototype is your internal representation of the most typical or relevant example of a category. It serves as a comparison standard when you use the representativeness heuristic to make judgments. For instance, your mental prototype of a Master Sommelier might include traits like sophistication and wine expertise, which you then use to evaluate whether someone fits that category.

The representativeness heuristic focuses on similarity to mental prototypes, whereas the availability heuristic decision making relies on how easily examples come to mind. While representativeness compares resemblance to a category, other shortcuts like anchoring adjust estimates from initial values, offering distinct pathways to judgment that can produce different errors.