EVIDENCE FOR A GRAMMAR-SPECIFIC DEFICIT IN CHILDREN

Background: Specific language impairment (SLI) is a disorder in which language acquisition is impaired in an otherwise normally developing c hild. SLI affects around 7% of children. The existence of a purely gra mmatical form of SLI has become extremely controversial because it poi nts to the existence and innateness of a putative grammatical subsyste m in the brain. Some researchers dispute the existence of a purely gra mmatical form of SLI. They hypothesise that SLI in children is caused by deficits in auditory and/or general cognitive processing, or social factors. There are also claims that the cognitive abilities of people with SLI have not yet been sufficiently characterised to substantiate the existence of SLI in a pure grammatical form. Results: We present a case study of a boy, known as AZ, with SLI. To investigate the claim for a primary grammatical impairment, we distinguish between grammati cal abilities, non-grammatical language abilities and non-verbal cogni tive abilities. We investigated AZ's abilities in each of these areas. AZ performed normally on auditory and cognitive tasks, yet exhibited severe grammatical impairments. This is evidence for a developmental g rammatical deficit that cannot be explained as a by-product of retarda tion or auditory difficulties. Conclusions: The case of AZ provides ev idence supporting the existence of a genetically determined, specialis ed mechanism that is necessary for the normal development of human lan guage. (C) Current Biology Ltd ISSN 0960-9822.