Generalization of treatment effects by young language-delayed children: a longitudinal analysis.

This study investigated the generalized effects of a language intervention program on the structural aspects of 8 language-delayed preschool children's productive language. Subjects were observed in preschool free play for periods ranging from 12 to 24 months concurrent with receiving daily didactic language intervention. A total of 57 two-, three-, and four-word syntactic forms were taught to criterion. Generalized usage was determined from (verbatim) language samples collected during free play periods in the subjects' classroom. Forty-two (74%) of the treated forms generalized to the subjects' spontaneous language in free play. There was a relationship between the complexity and potential functions of the treated forms and their generalization to free play. This effect may have been related to the subjects' MLUs. Substantial changes also occurred in the subjects' MLUs, frequency of speaking, Peabody Picture Vocabulary Test scores, and Houston Test for Language Development scores over the period of instruction. These measures suggested that 4 of the 8 subjects were functioning near the normal range at the conclusion of treatment. Implications of these and other results are discussed.