The influence of labels and facts on children’s and adults’ categorization

•We test how labels influence categorization while varying perceptual consistency.•We compare the influence of labels to observable and unobservable facts.•Labels influence formation of perceptually congruent and incongruent categories.•Facts as useful as labels for children and adults’ category formation.

Language has been assumed to influence categorization for both adults and children but the precise role and potency of linguistic labels in category formation remains open. Here we explore how linguistic labels help fit objects into categories when relevant perceptual information is either ambiguous or inconsistent with the labels. We also ask how the effects of labels compare to those of other types of information such as facts. We presented 4-year-old children and adults with tasks in which they had to categorize a perceptually ambiguous natural-kind stimulus with one of two equidistant standards (Exp. 1 and 2) or group an ambiguous natural-kind stimulus into a category with a perceptually dissimilar standard (Exp. 3). Participants had access to labels (e.g., “This one is a lorp/pim”), observable facts (e.g., “This one has a long/short beak”), or unobservable facts (e.g., “This one drinks water/milk”) that grouped the ambiguous stimulus with one of the standards. Both children and adults followed label- and fact-driven category boundaries for perceptually ambiguous stimuli (Exp. 1 and 2), and continued to do so even when the labels or facts pointed to perceptually incongruent categories (Exp. 3). These findings suggest a strong causal role for both labels and facts in categorization and have implications about theories of how categorization develops in children.