Maternal speech to normal and Down's syndrome children matched for mean length of utterance

The study was designed to provide data on the maternal linguistic environments of normal and Down's syndrome children at three levels of language development, as assessed by children's mean length of utterances (MLU). The three MLU levels were 1.00--1.50, 1.75--2.25, and 2.50--3.00, respectively. The subjects were 21 Down's syndrome children and their natural mothers and 21 normal children and their natural mothers. Normal children ranged in chronological age from 20 to 32 months and Down's syndrome children from 3 to 12 years. A one-hour verbal interaction between mother and child was tape recorded at home in a free-play situation. Maternal speech was analyzed using 20 measures related to its output-numerical, lexical, syntactical, semantic-structural, semantic-pragmatic, and language-teaching aspects. Additionally, eight measures of children's speech related to the output-numerical, lexical, syntactical semantic-structural aspects, and to imitativeness of maternal speech were computed as a means of testing the validity of the MLU-matching that forms a basis for this study. Except for the Type-token ratio, which favored Down's syndrome children, normal and Down's syndrome children were not found to differ. In contrast, there were numerous differences between the children in the different aspects of speech considered according to language level. None of the comparisons made of mother's speech to normal and to Down's syndrome children led to differences for any of the three children's language levels studied. It appeared that the maternal linguistic environments of language-learning Down's syndrome and normal children of corresponding MLU were similar in most respects. In contrast, there were numerous differences in mother's speech according to the language level of the children addressed. This confirmed that the expressive language level of the children is a far more powerful factor in influencing maternal speech than whether they are normal or Down's syndrome children. The implications of these findings were related to the delay-difference question in the language development of Down's syndrome children and to various interpretations of the effects of maternal linguistic input for language development and for intervention programs of language enhancement in the Down's syndrome child.