Normal and pathological development of subject-verb agreement in speech production: a study on French children

We report a study on the spoken production of subject-verb agreement in number by four age groups of normally developing children (between 5 and 8;5) and a group of 8 children with Specific Language Impairment (SLI; between 5;4 and 9;4), all French speaking. The production of verb agreement was experimentally elicited by asking children to complete sentence preambles containing a head noun and a potentially attracting 'local noun'. In contrast to previous studies that focused on attraction with local nouns within the subject constituent (postmodifiers), we also studied attraction with local nouns in structures that are not part of the subject constituent (interpolated adjuncts). In normally developing children, we report that (1) attraction effects appear from early on; (2) singular is produced as the default number until age 7 included; (3) more errors are produced with adjunct structures than with postmodifiers, but only from age 8;5 on. In contrast, even the older SLI children showed no attraction effect, a predominance of the singular as default, no effect of syntactic structure and, more generally, persistent high error rates. The turning point observed between 7 and 8;5 in normal children, characterized by a reduced error rate and a significant effect of syntactic structure, is interpreted as an index of the automatization of agreement. The syntactic structure effect is discussed in terms of the interplay of structural and working memory factors in the computation of long-distance relationships.