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.

No abstract

Categorical perception of a synthetic / r / -/ l / continuum was investigated with Japanese bilinguals at two levels of English language experience. The inexperienced Japanese group, referred to as Not-experienced, had had little or no previous training in English conversation. The Experienced Japanese group had had intensive training in English conversation by native American-English speakers. The tasks used were absolute identification, AXB discrimination, and oddity discrimination. Results showed classic categorical perception by an American-English control group. The Not-experienced Japanese showed near-chance performance on all tasks, with performance no better for stimuli that straddled the / r / -/ l / boundary than for stimuli that fell in either category. The Experienced Japanese group, however, perceived / r / and / I / categorically. Their identification performance did not differ from the American-English controls, but their overall performance levels on the discrimination tests were somewhat lower than for the Americans. We conclude that native Japanese adults learning English as a second language are capable of categorical perception of / r / and / I / . Implications for perceptual training of phonemic contrasts are discussed. » 1981 Cambridge University Press