MEASURING CHILDRENS LEXICAL DIVERSITY - DIFFERENTIATING TYPICAL AND IMPAIRED LANGUAGE LEARNERS

This study evaluated the extent to which measures of lexical diversity (type-token ratio and number of different words produced) differentia ted children with specific language impairment (SLI) from children who se language skills were following typical developmental expectations. Analysis of 50- and 100-utterance samples revealed that children with SLI did not significantly differ from their age- and language-equivale nt peers on type-token ratio; however, children with SLI did use signi ficantly fewer different words than their age-equivalent peers in thes e samples. When samples of 100 and 200 tokens were considered, the chi ldren with SLI also-used significantly fewer different words than thei r age-equivalent counterparts. Overall, the findings bf this study dis courage the use of type-token ratio, as traditionally calculated, in m any clinical and research activities related to children with SLI. In contrast, the number of different words produced provides a more sensi tive and informative estimate of lexical diversity.