Grammaticality judgements of an extended optional infinitive grammar: evidence from English-speaking children with specific language impairment.

This study reports on the outcomes of an investigation designed to evaluate competing accounts of the nature of the grammatical limitations of children with specific language impairment (SLI) with a new comprehension measure involving well-formedness judgments. It is a follow-up to the longitudinal study of Rice, Wexler, and Hershberger (1998), which reported on the production of grammatical morphemes by young children with SLI and 2 control groups of children, one at equivalent levels of mean length of utterance at the outset of the study, the other of equivalent age. In this investigation, we report on grammaticality judgment measures collected from the same 3 groups of children over a period of 2 years for 5 times of measurement. It is the first longitudinal study of grammaticality judgments of children with SLI. The findings show that children's grammatical judgments parallel their productions: Children with SLI can make fine-tuned grammatical judgments to reject morphosyntactic errors they are unlikely to commit, whereas they accept morphosyntactic errors that they are likely to produce. The findings support the extended optional infinitive (EOI) account of morphosyntactic limitation based in underlying grammatical representations and do not support accounts of input processing deficits or production constraints.