SPECIFIC LANGUAGE IMPAIRMENT AS A PERIOD OF EXTENDED OPTIONAL INFINITIVE

English-speaking children with specific language impairment (SLI) are known to have particular difficulty with the acquisition of grammatica l morphemes that carry tense and agreement features, such as the past tense -ed and third-person singular present -s. In this study, an Exte nded Optional infinitive (EOI) account of SLI is evaluated. In this ac count, -ed, -s BE, and DO are regarded as finiteness markers. This mod el predicts that finiteness markers are omitted for an extended period of time for nonimpaired children, and that this period will be extend ed for a longer time in children with SLI. At the same time, it predic ts that if finiteness markers are present, they will be used correctly . These predictions are tested in this study. Subjects were 18 5-year- old children with SLI with expressive and receptive language deficits and two comparison groups of children developing language normally: 22 CA-equivalent (5N) and 20 younger, MLU-equivalent children (3N). It w as found that the children with SLI used nonfinite forms of lexical ve rbs, or omitted BE and DO, more frequently than children in the 5N and 3N groups. At the same time, like the normally developing children, w hen the children with SLI marked finiteness, they did so appropriately . Most strikingly, the SLI group was highly accurate in marking agreem ent on BE and DO forms. The findings are discussed in terms of the pre dictions of the EOI model, in comparison to other models of the gramma tical-limitations of children with SLI.