Subject-Aux Inversion in Children with SLI.

An elicited production study investigated subject-aux inversion in 5-year-old children with specific language impairment (SLI) and 2 control groups, typically-developing 5-year-old children and 3-year-old children matched by mean length of utterance. The experimental findings showed that children with specific language impairment produced subject-aux inversion in yes/no questions significantly less often than either of the control groups. However, the fact that lack of inversion is reflected in the input led to the proposal that children with specific language impairment choose the most economical grammatical option. For main clause wh-questions, children with SLI carried out subject-aux inversion at a rate that was not significantly different from the control groups. This finding suggests that these children have access to hierarchical phrase structure representations for questions and the relevant movement operations. In embedded wh-questions, where subject-aux inversion is not permitted, children with SLI implemented SAI more frequently than the control groups. Our interpretation of this finding is that once children with SLI acquire the subject-aux inversion rule, that they are slower to learn that embedded clauses present an exception to the rule.