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ABSTRACT The speech of 6 mothers to their healthy infants was examined longitudinally during the neonatal period and at 4, 12, and 24 months in a semi-naturalistic setting. Features of speech analysed were: contour of fundamental frequency, repetitiveness, timing (durations of vocalizations and pauses), tempo and MLU. The neonatal period was characterized by elongated pauses. During the 4-month period the extent of pitch contouring and repetitiveness was greater than at earlier or later ages. By 24 months, the duration of vocalizations and length of MLU became markedly greater. The period of intense face-to-face interaction around the fourth month proved to involve more changes in certain prosodic features. Some of the possible functions of these changes during this phase are discussed.
Stern et al. (Tue,) studied this question.