This study examines the grammatical abilities of children and adolescents with Specific Language Impairment (SLI). There were two research goals. Firstly, the persistence of grammatical problems over time was examined by comparing a younger group of children with SLI and an older group of adolescents with SLI. Secondly, this study explored whether difficulties in the grammatical domain in SLI purely reflect a grammatical deficit or may partly stem from problems in the implementation of grammatical knowledge due to problems in information processing. In the grammatical production tasks, the complexity of the linguistic context was therefore varied to examine whether this would cause a (larger) decrease in scores in the SLI groups. In addition, different measures of information processing ability were administered and the link between variability in performance and processing abilities was examined.
On the basis of the outcomes this book makes two major claims. Firstly, grammatical problems in SLI are persistent into adolescence. For some grammatical aspects such as grammatical gender, fossilization seemed to take place before children reach adolescence. Other aspects, such as verb inflection, had clearly been acquired by adolescence but differences between SLI and typical development (TD) in the amount of errors still remained. Secondly, grammatical performance in SLI was affected by the linguistic context in which grammatical knowledge had to be implemented. Such effects were small or absent in the TD groups. The effect of context was related to the verbal processing abilities of the groups. Grammatical problems in SLI therefore do not always reflect a deficit in grammar. Even when grammatical knowledge has been acquired, a child or adolescent with SLI is not always able to implement this knowledge in performance.
This dissertation is of relevance to researchers in the fields of language acquisition and language disorders, as well as to clinicians and teachers working with children and adolescents with language impairments.