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).
Another example of profiling is the well-known model of reading impairments based on word recognition and linguistic comprehension, the two components of the simple view of reading popularized by Gough and Tunmer (1986). In this model, how well one reads (where reading is defined as comprehending what is read) depends on word recognition accuracy and general linguistic comprehension ability. The emphasis is on general comprehension (listening comprehension). A child with poor word recognition and adequate general comprehension would meet the classic definition of dyslexia (Catts & Kamhi, 2005). The opposite, a condition where a child has poor general comprehension but adequate word-reading ability, has been variously termed: specific comprehension deficit (Catts & Kamhi, 2005), poor comprehender (Cain & Oakhill, 2006), and hyperlexia (Aram, 1997). The child whose reading (and writing) skills are limited by poor general comprehension is an example of the importance of forming hypotheses about how listening and reading comprehension interact. A third possibility is the child with both problems—poor word recognition and poor general comprehension. This model of reading impairment has had a substantial impact on the way I conduct a language assessment and is one of the hypotheses that I often explore.
One profile of SLI advanced over a number of years is a form where the impairment is quite specific to select grammatical systems, namely, those that require complex mapping and dependency relations. Two major syntactic groups have emerged. In one account, the problem lies at the intersection of morphology and syntax within the verb system, blocking proper assignment of verb tense and agreement (Rice, 2002). Usually, the child omits the tense or agreement markers, resulting in sentences like “he bite him” (when telling a story about something happening in the past) or “he love his dog” (describing a general state of affairs). In another grammatical account of SLI, the focus is on structures described by long distance dependency relations found in structures such as passive voice, relative clauses, and WH questions (van der Lely, 2005; van der Lely, Rosen, & McClelland, 1998). To illustrate, in the following sentence there is a dependency relationship between bill and the “trace” that it leaves as a grammatical object in the embedded relative clause (shown at the point of the arrow) that must be represented before the sentence as a whole is comprehensible:
The bill that the House passed ↑ recently is unlikely to make it through the Senate in the same form.
Both of these specific, grammatically based varieties (morphosyntax and dependency relations) are the phenotypic outcomes of a domain-specific linguistic representational deficit. This deficit, in turn, is most likely genetically determined and resides in specialized cognitive processes that serve grammar (Silliman & Scott, 2006, p. 3). Even though the theoretical significance of these grammatical varieties of SLI is not universally accepted (Bishop, Adams, & Rosen, 2006), no one doubts that children with SLI find these specific structures to be problematic. Whether one adheres to a representational account or a domain-general cognitive-processing account (e.g., limited capacity processing) as the explanation of SLI, there would appear to be clinical utility in assessing these structures in comprehension and production tasks.
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