Categorization based on attribute versus relational similarity in 4- to 10-month-old infants

4- to 10-month-old infants were tested in 2 experiments to determine whether they used a similar attribute or a similar relationship among attributes to make visual judgments of similarity and categorization. In Exp. 1 infants were familiarized with a single stimulus composed of several attributes and a prescribed relationship among the attributes, left wing smaller than right wing. When tested in a novelty-preference procedure with novel stimuli that either preserved a single attribute but violated the relationship (Attribute Test Stimulus) or preserved the relationship with a new set of attributes (Relational Test Stimulus), 4-mo.-olds treated the Attribute Test Stimulus as familiar, whereas 6-mo.-olds treated the Relational Test Stimulus as familiar. Neither 8- nor 10-mo.-olds showed a preference for either test stimulus. In Exp.2 a category containing 3 exemplars was constructed. In each exemplar a single attribute, left wing, was held constant, and all 3 exemplars shared the same relational structure, left wing smaller than right wing, but the remaining attributes varied across exemplars. Four, 6-, and 8-mo.-olds in Exp. 2 reliably included the novel Attribute Test Stimulus in the category. These data suggest that, although infants under 8 months can recognize relational information, they may not always use that information when making categorization judgments, particularly if a single, well-defined attribute is available as the basis for categorization.