Argument structure in Specific Language Impairment : from theory to therapy
This thesis is in two parts: the first focuses on theories of SLI and the development of argument structure while the second focuses on intervention. Chapter 1 reviews experimental findings and theories of SLI and finds that while some areas of language are well-researched, others (including argument structure) have received relatively little attention. Chapter 2 reviews the literature regarding the development of argument structure and concludes that studies of typical development have not investigated use of alternations and omissions of obligatory arguments, whereas studies of SLI have little focus on alternations or overgeneralisations. Chapters 4 and 5 therefore consider the performance of typically developing children and children with SLI on all these areas. I find typically developing children differ from adults in their use of the causative alternation and overgeneralisation of the locative alternation. The children with SLI have difficulties with argument structure, avoiding the ditransitive form of the dative alternation and making more errors with change of state verbs and omission of arguments. A secondary focus (Chapter 6) is on the influence of phonological complexity and length (measured by a non-word repetition test) on the language abilities of children with SLI. The results show a bimodal split where half the children with SLI show normal abilities and half have significant difficulties. Chapter 7 discusses the implications of the experimental findings for theories of SLI. Part 2 reviews intervention studies for SLI (Chapter 8) and presents an intervention study focusing on argument structure (Chapter 9). 27 secondary-aged children with SLI are randomly assigned to three groups, one control and two target therapies focusing on semantics vs constructions. Both target groups show significant progress. Thus, this thesis shows that detailed investigations of the nature of the deficit in SLI can lead to successful interventions even for children with severe, persistent difficulties.