This research describes the development of phrase-final prosodic patterns in nine English-speaking children. The intonation feature of interest is the fall in the fundamental frequency of the voice that occurs in the final syllables of statements. The corresponding feature of speech timing is phrase-final lengthening. To test opposing theories about the relationship between intonation and syllable timing, these boundary features were compared in a longitudinal study of the children’s speech development between the mean ages of 16 and 25 months. The results suggest that young children acquire the skills that control intonation earlier than final syllable timing skills. The findings support the hypothesis that final lengthening in the speech of 2-year-olds is a learned prosodic feature that cannot be accounted for as a secondary effect of inherent speech production constraints. In addition, a consistent pattern of final lengthening began to emerge when the children were making the transition to combinatorial speech, suggesting a developmental relationship between the child’s learning of speech timing and syntax.

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The purpose of this study was to describe the pattern in which English-speaking children acquire intonation. A second goal was to account for emerging intonation from a theoretical perspective. Six groups of 10 children each between the ages of 6 and 23 months participated in individual play sessions with their mothers and an experimenter. Pitch contours were acoustically analyzed in monosyllabic utterances produced by each child. The observed nonlinear shape of intonation development suggested a linguistically based pattern of regression and reorganization. However, the precocious expression of intonation in the youngest infants also pointed to the role of physiological universals and emotional experience. It is concluded that children's early intonation reflects biological, affective, and linguistic influences.

This study focuses on the potential role of prosodic "boundary features" in developmental disorders of morphosyntax. As exemplified melodically by the final portion of the falling tone and rhythmically by final syllable lengthening, boundary features mark the right edge of major constituent units in speech and thus phonetically reflect syntactic structure on the level of clauses and sentences. To resolve conflicting findings about the development of boundary features in children with specific language impairment (SLI), this study describes the falling tone and final syllable lengthening in the spontaneous speech of 10 four-year-old children with the phonologic-syntactic type of SLI and 10 four-year-old children with normal language development. The results--indicating that some prosodic boundary features are normal in preschoolers with SLI--show that impairments of morphology and syntax on the segmental level of the grammar do not implicate systematic deficits in syntax-sensitive features on the suprasegmental level. The potential dissociation between prosodic and morphosyntactic development is shown most clearly by the remarkable robustness of the falling tone, which was observed in 9 of the 10 children with SLI, in spite of the moderate to severe deficits they demonstrated in segmental phonology, morphosyntax, and mean length of utterance.