The Emergence of an Abstract Grammatical Category in Children's Early Speech.

How do children begin to use language to say things they have never heard before? The origins of linguistic productivity have been a subject of heated debate: Whereas generativist accounts posit that children's early language reflects the presence of syntactic abstractions, constructivist approaches instead emphasize gradual generalization derived from frequently heard forms. In the present research, we developed a Bayesian statistical model that measures the degree of abstraction implicit in children's early use of the determiners "a" and "the." Our work revealed that many previously used corpora are too small to allow researchers to judge between these theoretical positions. However, several data sets, including the Speechome corpus-a new ultra-dense data set for one child-showed evidence of low initial levels of productivity and higher levels later in development. These findings are consistent with the hypothesis that children lack rich grammatical knowledge at the outset of language learning but rapidly begin to generalize on the basis of structural regularities in their input.