Abstract :
Phonology is bimodular: prosody (relational aspects) and melody (‘phonetic’ aspects) are to some extent autonomous in steady-state (adult) language. Therefore the acquisition of individual melodic and prosodic modules and their subsequent orientation with respect to one another must constitute three different developmental tasks. The acquisition of melodic primes may take place independently of any other process. If infant perception has this kind of phonological import, then disparate phonetic reflexes which are predicted as phonologically identical might show parallels in acquisition. In Government Phonology, general theory argues that the same abstract melodic objects underlie both laryngeal contrasts in stops and lexical tonal contrasts. Earlier studies show that language-specific attunement to stop contrasts has taken place by the age of six to eight months. Tests on lexical tone perception are now reported, using both adults and infants. The results show that at around six months of age, babies acquiring Yorùbá, a language which has a three-way contrast for tone, attend more closely to pitch changes within the minimal domain word than do English controls. Further, they only attend to those pitch changes that possess phonological import within that domain in the steady-state language. In this their perception exactly parallels that displayed by the adult speakers. Finally, both adults and infants display a particular asymmetry in perception in that they discriminate the high/mid tone distinction but fail to perceive the mid/low contrast where no linguistic context is present. This was not predicted at the onset of testing, but it is argued that it may well have a phonological explanation, which could align this finding with the typological asymmetries to be found in the distribution of lexical tone in Yorùbá and other west African languages.
