Environmental correlates of child copula verb growth

A recurring result from studies which relate the frequency of input variables to rate of language development, is the link between auxiliary verb growth and yes-no questions addressed to children. Explanations for this relationship usually concentrate on the advantages of hearing stressed and non-contracted auxiliary forms in sentence-initial position over hearing unstressed, contracted forms in medial position in declaratives. If such accounts are correct, then it can be predicted that yes-no questions which place forms of COPULA be in initial position will also increase the rate of growth of children's COPULA verb development. This prediction was tested using a sample of 33 children, carefully matched for stage of language development at 1;9 and 2;0 years; rate of copula verb growth was then measured over the succeeding nine months. Analyses include an examination of the contribution of sub-categories of yes-no question, tag questions, and utterances containing sentence-final copulas to the growth of contracted and full copulas. Results confirm that the frequency of inverted copulas in yes-no questions predicts children's copula development. Nevertheless, caution is urged before interpreting the relationship in terms of a direct causal model.