Grammatical Impairment: An Overview
and a Sketch of Dutch
Jan de Jong
University of Utrecht
A casual inspection of the recent literature on specific language impairment (SLI) in children suggests that these children's core difficulties are exclusively in the area of grammatical morphology. This impression is misleading. Although no classification of SLI is universally accepted, the subgroup from which subjects in studies on SLI are most often recruited shows grammatical symptoms often accompanied by phonological symptoms—they belong to the so-called phonological-syntactic subtype. Although this subtype harbors the largest number of language-impaired children, it is not the only one—there are various subtypes of SLI, although some are more common than others (Conti-Ramsden et al., 1997; Haynes & Naidoo, 1991; Rapin & Allen, 1983).
Although SLI is heterogeneous, difficulties with grammatical morphology are indeed seen as a hallmark of SLI. This was shown recently in a report from a workshop that aimed to define a phenotype for SLI at large. In this report, Tager-Flusberg and Cooper (1999) named two measures that are promising in their capacity to determine whether a child has SLI. One is nonword repetition, and the other is the child's ability to mark finiteness on the verb. This observation echoes previous suggestions that impaired inflectional morphology is a clinical marker of SLI (Rice & Wexler, 1996).
There is another reason—besides its status as a key symptom—that SLI children's poor handling of grammatical morphology receives much scientific attention. This has to do with the theoretical issues raised by the morphological symptoms. Mastery of grammatical morphemes appeals to