Concepts cluster by family resemblance, not strict definitions

Correct: B — Family-resemblance structures whose members share overlapping but non-defining features

Rosch & Mervis (1975) demonstrated that prototypicality ratings within a category (e.g., 'robin' vs. 'penguin' for 'bird') correlate strongly with the number of features a member shares with other members of the same category and the number of features it does not share with contrasting categories. Natural categories thus exhibit graded, family-resemblance structure rather than crisp definitional boundaries. This empirical work, alongside Eleanor Rosch's broader prototype theory, displaced classical 'necessary and sufficient features' accounts and reshaped how psychology, linguistics, and computer science model concepts and category learning across many domains.