Language Impairment Categories and Profiles
by Perhaps the most basic question about language impairment is whether it stands alone as a child’s only problem or, on the contrary,there are additional problems—a distinction captured in the literature as primary or secondary (Law, Garret, & Nye, 2004; Nelson,2010).
Children with primary language impairments are otherwise typical in cognitive, sensory, medical/neurological, and social–emotional domains. Secondary language impairments are those in which a language difficulty exists alongside problems in these other domains. Use of the term secondary is unfortunate because it seems to imply that the language impairment is of secondary importance to the other condition, for example autism, when in fact the language impairment is often one of the most problematic features of a child’s entire profile. Nevertheless, the distinction is important because it channels our attention immediately to a body of research that addresses distinguishing linguistic features of children in particular groups. For example, children with Down syndrome are known to have syntactic difficulties that exceed predictions based on mental age (Abbeduto & Chapman, 2005) whereas lexical (vocabulary)skills are relatively higher (Laws & Bishop, 2003)-–a pattern that differs for children with Fragile X syndrome (Abbeduto, Brady,& Kover, 2007). In studies involving children with autism who are verbal but language impaired, Kjelgaard and Tager-Flusberg (2001)report profiles resembling children with specific language impairment (SLI). Both groups are especially poor on grammatical tasks and have difficulty repeating long sentences and nonwords correctly.
Grammatical impairment, in particular tense marking, has long been considered as a clinical marker of children with the primary condition known as specific language impairment (Leonard, 1998; Rice, 2007)—one that “surfaces” again when these children are asked to write, even though their speech is practically error free (Windsor, Scott, & Street, 2000). A large body of research on the linguistic features of SLI and an emerging literature on language characteristics of children with known syndromes provide a starting point in the hypothesis-testing process by pointing to patterns of relative strength and weakness that could be encountered. Refinements are expected as researchers continue to make progress defining the phenotypic linguistic behaviors associated with genetic findings in various groups (e.g., Hayiou-Thomas, Harlaar, Dale, & Plomin, 2010; Rice, Smith, & Gayán, 2009).
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