DIFFERENTIATING SPECIFIC LANGUAGE IMPAIRMENT FROM NORMAL LANGUAGE-DEVELOPMENT USING GRAMMATICAL ANALYSIS

The present investigation sought to determine whether preschool childr en with specific language impairment (SLI) could be differentiated fro m an age-matched sample of typically developing children on the basis of grammatical features displayed within a 20-min sample of conversati onal language. Language samples from 47 children, 24-50 months of age, described in a previous study (Klee, Schaffer, May, Membrino and Moug ey (1989) were analysed using the LARSP framework (Crystal, Fletcher a nd Garman, 1989). Composite variables were created from the original L ARSP categories and transformed into ratios to adjust for the differin g number of utterances in each transcript. A discriminant function whi ch optimized the differences between the two groups was then derived f rom the grammatical analysis. In addition to age and a constant, the f unction contained three linguistic variables: stage I-major utterances , three-element NPs and VP errors. The outcomes of the discriminant fu nction and the clinical diagnosis were in agreement in 91.5% of the ca ses. The predictive validity of the discriminant function was then eva luated in a field test employing a second sample of children (n=37). T he outcome of the discriminant function concurred with the clinical di agnosis in 86.5% of the new cases.