ABSTRACT

Purpose: Children acquiring English use copula forms in formulaic constructions (e.g., it’s) before using copula forms accurately with a variety of sentence subjects. Children may be susceptible to relying on copula forms learned by rote when the copulas they hear in parent input are frequently formulaic. Methods: In this investigation, copulas in parent input to typically developing, English-speaking toddlers were classified by whether they were contracted to the sentence subject and by whether that subject was pronominal or lexical. Children’s growth in copula productivity between 27 and 33 months of age was measured by quantifying combinations of copula am, are, is, was, and were with unique subjects. Results: Parents’ use of copula is with contraction to pronominal subjects outnumbered uses with lexical subjects or without contraction. Parents’ use of the less common copulas, with low-frequency lexical subjects or without contraction to the subject, was significantly positively related to children’s subsequent growth in unique subject+copula combinations. However, parents’ use of copulas contracted to pronouns was not related to children’s copula productivity. Conclusions: These findings hold implications for understanding how children make use of grammatical information in parent input, for how to measure children’s grammatical growth, and for enhancing the copula input provided by clinicians and parents.