Clarifying the role of shape in children's taxonomic assumption.

When asked to find a new referent of a novel label children tend to ignore thematic relations (e.g., the relation between a spider and its web) and focus instead on taxonomic relations (e.g., the relation between a spider and a snake). The precise nature of children's taxonomic assumption has not been clear, however. One possibility is that the taxonomic assumption reduces to a "similar-shape rule": perhaps children tend to select objects of the same taxonomic kind when asked to extend new labels simply because these objects are more similar in shape than objects which are only thematically related. Sixty children between 3 and 5 years of age participated in three studies which examined children's attention to thematic relations, similarity of shape, and taxonomic relations when extending novel object labels. The findings indicated that shape has some primacy in children's expectations about object label reference, yet when shape is not available as a guide, children also take taxonomic kind into consideration when searching for new referents of novel labels. Thus children make use of a relatively rich and somewhat varied set of expectations to guide their inferences about object label reference.