Wednesday, November 6, 2013

What Causes Specific Language Impairment in Children?

Bishop, D.V. (2006). What causes specific language impairment in children? Current Directions in Psychological Science, 15 (5), 217-221.

This week’s article is an update of Bishop’s "The underlying nature of specific language impairment" discussed in the last posting looking at the more broad hypotheses of genetic vs. multiple underlying defictis as explanations for SLI.

            Studies showing that SLI runs in families suggest a genetic influence; however these results can be confounded by the fact that families share environments. Twin studies have been used to test this idea and have shown that monozygotic twins have more similar SLI profiles than dizygotic twins. Nevertheless, SLI does not follow a simple inheritance pattern suggesting that there is no ‘gene for language’. Rather, SLI may be described as a complex genetic disorder, that is, a disorder of several genes interacting with environmental factors. Indeed, Bishop’s own twin studies have provided evidence of separable genetic influences on a phonological short-term memory task (non-word repetition), and a grammatical task (adding inflectional ending to verbs), but not on an auditory perception task.  

            Overall, children with multiple deficits were more likely to be identified as SLI. Multiple routes to language acquisition may provide a protective factor such that redundancies and compensations occur in the system even if a single weakness or deficit exists. Multiple deficits, however, would impair language learning and may result in identification as SLI.

Future directions will continue to examine the development of language abilities over time, and investigate genetic and environmental interactions. 

Blogger: Lauren Perduk is currently completing her Masters of Clinical Science in Speech Language Pathology. She often participants in lab meetings with the Language and Working Memory lab. 

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