Text exposure predicts spoken production of complex sentences in 8- and 12-year-old children and adults.

There is still much debate about the nature of the experiential and maturational changes that take place during childhood to bring about the sophisticated language abilities of an adult. The present study investigated text exposure as a possible source of linguistic experience that plays a role in the development of adult-like language abilities. Corpus analyses of object and passive relative clauses (Object: The book that the woman carried; Passive: The book that was carried by the woman) established the frequencies of these sentence types in child-directed speech and children's literature. We found that relative clauses of either type were more frequent in the written corpus, and that the ratio of passive to object relatives was much higher in the written corpus as well. This analysis suggests that passive relative clauses are much more frequent in a child's linguistic environment if they have high rates of text exposure. We then elicited object and passive relative clauses using a picture-description production task with 8- and 12-year-old children and adults. Both group and individual differences were consistent with the corpus analyses, such that older individuals and individuals with more text exposure produced more passive relative clauses. These findings suggest that the qualitatively different patterns of text versus speech may be an important source of linguistic experience for the development of adult-like language behavior.