Abstract:
Children with specific language impairment (SLI) have particular problems with grammar, despite normal intellectual and other sensory skills. Several theories have been proposed to explain the cause of language deficits in the SLI population. The present review reinforces the proximal procedural deficit hypothesis by Ullman and Pierpont (2005) as a convincing cause of grammatical deficits in SLI, against the theories of distal processing and memory capacity deficiency, which have several drawbacks in explaining grammar problems in SLI. In this review, evidence is brought together from Chomsky’s transformational levels (to mimic SLI language characteristics), genetics of SLI (FOXP2), neuro-anatomy of the procedural memory system, and evolution of FOXP2 to support the view that the procedural memory system on which grammar is overlaid is an evolutionary product which is affected in children with SLI. We call attention to the fact that grammar deficits in SLI could be better explained if this is viewed as an evolutionary default leading to deficits in syntax domain (mainly because of procedural deficits). The proposed view is testable as per the directions proposed in the review