Lexical and grammatical development were strongly related in both groups, consistent with the single-mechanism account of language acquisition. The results were mixed in terms of finding longitudinal differences in lexical-grammatical relationships between the TD and late-talking children; however, several analyses suggested that for late-talking children, syntactic growth may be less facilitative of lexical development.

This study investigated fast mapping in late-talking (LT) toddlers and toddlers with normal language (NL) development matched on age, nonverbal cognition, and maternal education. The fast mapping task included novel object labels and familiar words. The LT group performed significantly worse than the NL group on novel word comprehension and production, as well as familiar word production. For both groups, fast mapping performance was associated with concurrent language ability and later language outcomes. A post hoc analysis of phonotactic probability (PP) and neighborhood density (ND) suggested that the majority of NL toddlers displayed optimal learning of the nonword with low PP/ND. The LT group did not display the same sensitivity to PP/ND characteristics as the NL group.

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Purpose The purpose of this study was to test Bedore and Leonard’s (1998) proposal that a verb morpheme composite may hold promise as a clinical marker for specific language impairment (SLI) in English speakers and serve as an accurate basis for the classification of children with and without SLI beyond the preschool level. Method The language transcripts of 50 school-age children with SLI (Mage = 7;9) and 50 age-matched typically developing peers (Mage = 7;9) were analyzed. Following the Bedore and Leonard procedure, three variables were measured: mean length of utterance in morphemes (MLU-morphemes), a noun morpheme composite, and a finite verb morpheme composite. Results Overall findings indicated that neither grammatical morpheme composite alone adequately discriminated the groups at this developmental level. Combining the noun and verb grammatical morpheme composite measures with MLU-morphemes resulted in good discriminant accuracy in classifying subgroups of the youngest children with and without SLI in the school-age sample. Conclusions We did not find that verb morphology alone served as a useful clinical marker of SLI in school-age children. Potential explanations for these findings and ideas for future research are discussed.

This paper is NOT THE PUBLISHED VERSION; but the author's final, peer-reviewed manuscript. The published version may be accessed by following the link in the citation below.