Abstract
BACKGROUND: Surprisingly little is known about the use of modal auxiliaries by children with specific language impairment (SLI). These forms fall within the category of grammatical morphology, an area of morphosyntax that is purportedly very weak in children with SLI. AIMS: Three studies were conducted to examine the use of modal auxiliaries by preschool-aged children with SLI. METHODS & PROCEDURES: In each study, probe tasks were designed to create contexts that encouraged the use of modals to express the modality functions of ability and permission. In Studies 1 and 3, English-speaking children participated. In Study 2, the participants were Cantonese-speaking children. In each study, three groups of children participated: A group exhibiting SLI, a group of younger typically developing children (YTD), and a group of (older) typically developing children (OTD) matched with the SLI group according to age. OUTCOME & RESULTS: In Study 1, English-speaking children with SLI were as proficient as YTD children, though less proficient than OTD children in the use of the modal can to express the modality functions of ability and permission. In Study 2, the same modality functions were studied in the speech of SLI, YTD and OTD groups who were speakers of Cantonese. In this language, tense is not employed, and therefore the modality function could be examined independent of formal tense. Results similar to those of Study 1 were obtained. Study 3 again studied SLI, YTD and OTD groups in English to determine whether the children's expression of ability differed across past (could) and non-past (can) contexts. The results for can replicated the findings from Study 1. However, the children with SLI were significantly more limited than both the YTD and OTD groups in their use of could. CONCLUSIONS: The results suggest that most children with SLI have access to modality functions such as ability and permission. However, the findings of Study 3 suggest that they may have a reduced inventory of modal forms or difficulty expressing the same function in both past and non-past contexts. These potential areas of difficulty suggest possible directions for intervention.