Investigations of syntactic knowledge in question structures in children with specific language impairment

Children with specific language impairment (SLI) are a group of children who are known for their language difficulties despite a clean bill of health in all other aspects of development. It is now widely accepted that tense morphology is particularly affected in children with SLI, but the extent of the language deficit, especially in the area of syntactic knowledge, is not yet known. There is some literature in English and across languages showing that children with SLI have difficulties with the syntactic operations that are required to form and comprehend questions. However, it is not clear, at least from the production data, whether this finding is limited to a subgroup of children labelled Grammatical SLI (G-SLI) whose grammatical deficit is particularly severe, or whether this finding extends to a general population of children with SLI. To understand this important question, this thesis by publication explores three aspects of children's syntactic knowledge in question structures, comparing children with SLI with two control groups, an age-matched group and a group matched by MLU. This thesis is structured as follows : Chapter one provides background information and describes the theoretical framework upon which this thesis is based. The motivation for the studies reported in Chapters two through to Chapter five is discussed. Chapter two investigates aspects of morphology, syntax and pragmatics in children with SLI's answers to wh-questions. The aim of this study is to investigate whether the impairment is seen in different language components. The study revealed that children with SLI demonstrated the reported difficulty with using tense, while demonstrating that they had no difficulty computing the appropriate syntactic structures. Chapter three is a production study that investigated the syntactic rule of Subject-Aux Inversion (SAI) in main clauses and also in embedded clauses (where it is prohibited). This study found that the SAI rule is delayed for children with SLI, but once they have learned the rule, children implement it well. The striking finding is that the children with SLI who implement the rule implement it too well, and extended it to embedded clauses. This group has difficulty inhibiting the rule. Chapter four evaluates the adherence to the linguistic constraint on contraction in questions. The aim of this study is to investigate whether children with SLI have the same underlying grammar as typically developing children in this aspect of linguistic knowledge which is often claimed to be universal. The experimental findings showed that the children with SLI respected the constraint well, and were not different from the control groups. Chapter five concludes the thesis by summarising the experimental findings from the studies in the three chapters. The experimental results observed in three studies together provide evidence that children with SLI do not have difficulties in every area of language, and in fact, show strength in some areas of syntactic knowledge in their question structures.