Lexical Diversity Versus Lexical Error in the Language Transcripts of Children With Developmental Language Disorder: Different Conclusions About Lexical Ability.

Purpose The purpose of this study was to provide preliminary data on differences in lexical diversity and lexical-semantic errors in the language samples of children with developmental language disorder (DLD) and children with typical language development (TLD) of the same age. Method We analyzed word use in the narrative transcripts of children with DLD and TLD (N = 14; M = 6;8 [years;months]) using standard measures of lexical diversity (number of different words, moving-average type-token ratio) and additional counts of lexical-semantic errors. Results There were no significant differences between the groups in lexical diversity, and all children with DLD scored within the age-appropriate range on diversity relative to a normative sample. The children with DLD, however, produced significantly more lexical errors than their TLD peers. Conclusions The results suggest that caution is warranted when interpreting normal-range lexical diversity scores in children with DLD, as children with DLD may demonstrate functional difficulties with word use that are not captured by lexical diversity measures. A focus on lexical errors holds promise for characterizing lexical-semantic qualities of language transcripts that are not captured by standard measures of diversity. Development of a reliable clinical system for coding and characterizing lexical-semantic errors in language transcripts is warranted.