Past-tense marking by children with and without specific language impairment.

This study examined the productivity and representation of past-tense marking in children with and without specific language impairment (SLI). Participants were 11 6-year-olds with SLI, 11 age-matched controls, and 11 MLU-matched controls. Regular and irregular verbs were used to examine the productivity of regular marking. Past-tense representation was examined by asking children to inflect homophonous pairs of denominal and irregular root verbs. All three groups demonstrated productive marking of past tense, although as expected the accuracy of the impaired groups was less than that of earlier control group. Patterns of past-tense marking as a function of a word's phonological composition and inflectional frequency were the same for the SLI- and MLU-matched groups, and all children presented a past-tense system that was sensitive to grammatical structure. The findings replicate previous research of the SLI morphological system and provide additional specification of these children's morphological strengths and weaknesses. Strengths include the children's sensitivity to grammatical and phonological characteristics of the lexicon; weaknesses include limited productivity of regular past-tense marking and a greater sensitivity to frequency manipulations as compared to normally developing children. Results are discussed in terms of the nature of the SLI profile. They also are used to evaluate the theoretical model on which the study was based.