A single word in a population of words.

Carey and Bartlett introduced a new method for studying lexical development, one of presenting the child with a word and a single context of use and asking what was learned from that one encounter. They also reported a then new finding: By using what they already knew about previously learned words, young children could narrow the range of possibilities for likely meanings in a single encounter. This papers honors that original contribution and the robust literature and set of phenomena it generated by considering how newly learned categories must fit into a population of already learned categories. This paper presents an overview of Packing Theory, a formal geometrical analysis of how local interactions in a large population of categories create a global structure of feature relevance such that near categories in the population of have similar generalization patterns. The implications of these ideas for learning from a single encounter, their relation to the evidence of artificial word learning studies, and new predictions are discussed.