Functional categories in the grammars of children with specific language impairment.

Children with specific language impairment often show a serious limitation in their use of grammatical morphemes such as verb inflections and free-standing closed-class forms. The purpose of this study was to determine whether such difficulty constitutes a problem with entire functional categories. Examination of the spontaneous speech of a group of 10 English-speaking children with specific language impairment revealed clear evidence of each of the functional categories examined: Determiner, inflection, and Complementizer. However, relative to younger normally developing children with comparable mean utterance lengths, these children showed lower percentages of use of many of the grammatical elements associated with these functional categories. The utility of employing a functional category framework in the study of specific language impairment and the implications of the findings for other accounts of this disorder are discussed.