Functional Categories and Specific Language Impairment: A Case Study.

Children with specific language impairment (SLI) who are acquiring English often show a more serious deficit in grammatical morphology than in other areas of language. Because most grammatical morphemes appear to be associated with functional categories such as Determiner (Det), Comple? mentizer (Comp), and Inflection (Infl), these extraordinary deficits in gram? matical morphology might be attributable to a pronounced delay in the acquisition of these categories or to an underlying grammar that lacks them. In this article, we examined the status of the functional categories Det, Comp, and Infl in the grammar of one child with SLI seen at four ages: 3;9,4;3, 4;5, and 5;2. The results were consistent with an interpretation of a slowly developing grammar with elements from functional categories especially late in emergence and protracted in development.