The influence of argument-structure complexity on the use of auxiliary verbs by children with SLI.

The purpose of the present study was to investigate the influence of argument-structure complexity on the omission of auxiliary be verbs in a group of children with specific language impairment (SLI). These children were compared to a group of younger, normally developing children matched for mean length of utterance (MLU) and a group of children matched for chronological age (CA). Using a story-completion task, the children (N = 30) were required to produce sentences of varying length and argument-structure complexity. The results of the study indicated that the children with SLI omitted more auxiliary forms than either the MLU or CA controls. In addition, both the children with SLI and the MLU controls were more likely to omit the auxiliary forms when attempting sentences with greater argument-structure complexity. These results suggest that argument-structure complexity may be a contributing factor to children's omissions of grammatical morphemes.