Similarity has been cast both as hero and as villain in theories of cognitive processing, and the same is true for cognitive development. On the positive side, Rosch and her colleagues have suggested that similarity is an initial organizing principle in the development of categorization (e.g., Rosch, Mervis, Gray, Johnson, & Boyes-Braem, 1976), and Carey (1985) implicates a similarity mechanism in children's learning of the biological domain. It has also been suggested that similarity may play a role in word acquisition (Anglin, 1970; Bowerman, 1973, 1976; E. V. Clark, 1973; Davidson & Gelman, 1990; Gentner, 1982c). Others have taken a more pessimistic view, according to which similarity is either a misleading or at best an inferior strategy used as a last resort. Keil (1989), for example, posits that children begin with theories of the world and that similarity functions merely as a fallback strategy to be resorted to when theory fails.

A related issue is the course of development of similarity. Many researchers have suggested that children's use of similarity changes from an early and naiïve form to a later, more enlightened form.