A comparison of verb use in children with SLI and their younger siblings

The present longitudinal study examined the use of verbs at the early stages of expressive language development by children with specific language impairment (SLI). Three children with SLI and their younger normal language learning siblings were videotaped during mother-child interactions in the home over a 2-year period. At the beginning of the study both the child with SLI and the younger sibling appeared to be in the same stage of expressive language development as measured by mean length of utterance (MLU). Thus, the younger sibling acted as a control for the child with SLI. Results indicate on the one hand no consistent significant difference in the proportion of verb types used by children with SLI and their younger siblings across the developmental period studied. On the other hand, the younger siblings all used significantly greater proportions of verb tokens than their impaired SLI brothers after a particular point in development. Comparison of particular verbs used suggest that children with SLI have difficulties applying the verbs in their lexicon across contexts. The normal younger siblings used a wider variety of verb forms in their constructions containing verbs and they also used similar forms for different verbs which the children with SLI did not do or did so to a lesser extent. The findings are discussed and, in particular, two hypotheses are proposed: an 'SLI critical mass' hypothesis following the work of Marchman & Bates (1994) and an 'Extended Verb-island' hypothesis following the work of Tomasello (1992).