Sources of individual differences in the acquisition of tense inflection by English second language learners with and without specific language impairment

The goal of this study was to investigate whether individual difference factors influence the second language (L2) learning of children with specific language impairment (SLI) and children with typical development (TD) differently. The study focuses on tense inflection development in English L2 children. The roles of age of L2 acquisition, length of L2 exposure, and first language (L1) were examined. Twenty-four pairs of 4- and 5-year-old English L2 children with SLI and English L2 children with TD participated in the study. Children's responses on the third person singular and regular past tense probes of the Test of Early Grammatical Impairment (Rice & Wexler, 2001) were analyzed using logistic mixed regression modeling and classification procedures. For all children, those who started learning English later performed better than children who started learning English earlier, but the advantage of an older age of acquisition was particularly present in the L2 with SLI group. For children in the L2 group with TD, their accuracy with tense inflection clearly increased with longer L2 exposure, but this was not found for the L2 children with SLI. Finally, L2 children with TD were better able to transfer L1 knowledge than L2 children with SLI