The role of the input in the acquisition of third person singular verbs in English.

During the early stages of language acquisition, children pass through a stage of development when they produce both finite and nonfinite verb forms in finite contexts (e.g., "it go there," "it goes there"). Theorists who assume that children operate with an abstract understanding of tense and agreement marking from the beginnings of language use tend to explain this phenomenon in terms of either performance limitations in production (e.g., V. Valian, 1991) or the optional use of finite forms in finite contexts due to a lack of knowledge that tense and agreement marking is obligatory (the optional infinitive hypothesis; K. Wexler, 1994, 1996). An alternative explanation, however, is that children's use of nonfinite forms is based on the presence of questions in the input ("Where does it go?") where the grammatical subject is immediately followed by a nonfinite verb form. To compare these explanations, 2 groups of 24 children aged between 2 years 6 months and 3 years were exposed to 6 known and 3 novel verbs produced in either declaratives or questions or in both declaratives and questions. The children were then questioned to elicit use of the verbs in either finite or nonfinite contexts. The results show that for novel verbs, the children's patterns of verb use were closely related to the patterns of verb use modeled in the language to which they were exposed. For known verbs, there were no differences in the children's use of individual verbs, regardless of the specific patterns of verb use modeled in the language they heard. The implications of these findings for theories of early verb use are discussed.