Children's theories of word meaning: The role of shape similarity in early acquisition

This research contrasts two important proposals as to children's assumptions about word meanings: the taxonomic assumption proposal and the shape bias proposal. Both proposals agree that children focus on groups of "like kind" in word meaning extension, but they differ in their assumption as to the nature of "likeness" for young children. We tested the two proposals by separating and comparing category membership and perceptual similarity in a word/no-word match-to-sample task. Two age groups of children, 3- and 5-year-olds, were shown a standard picture (e.g., an apple) and three other pictures: a taxonomically similar object (e.g., a banana), a perceptually similar object (e.g., a ball) and a thematically related object (e.g., a knife). They were asked either: "This is a dax; show me another dax" or "Find the one that goes with this one." There were two main results. First, both age groups showed a pronounced shift from thematic-based to shape-based responding when novel words were given. Second, a developmental shift was found from shape responding to taxonomic responding in the presence of a novel word. These results suggest that perceptual similarity (in particular, shape similarity) is very important in early word meaning, but that children gradually shift their attention to deeper properties. We conjecture that this early focus on perceptual similarity may help young children learn categories, gradually bootstrapping them to a sense of taxonomic relations that goes beyond perceptual similarity.