Three-year-olds' production of Australian English phonemic vowel length as a function of prosodic context.

Durational contrasts are used not only to signal phrasal boundaries and focused constituents, but also to make phonemic distinctions. Boundary and focus effects can therefore interact with phonemic length contrasts, presenting a challenge for learners. Boundary effects are most clearly seen in the syllable rhyme, where the nucleus and coda are longer in utterance-final compared to utterance-medial position, the magnitude of lengthening diminishing leftward from the end of the word. In the case of focus, where the nucleus and coda are also lengthened, the magnitude of lengthening diminishes rightwards toward the end of the word. The goal of this paper was therefore to compare productions of the phonemic vowel length contrast /ɐː/ vs /ɐ/ in adults and 3-yr-old children learning Australian English in the face of competing demands from boundary and focus lengthening. The results showed that the children maintain the /ɐː/ vs /ɐ/ contrast across prosodic contexts. They are also able to implement an adult-like pattern of boundary-related lengthening, but are still developing focus-related lengthening. The findings suggest that these 3-yr-olds have good command of the phonemic vowel length contrast, but are still fine-tuning language-specific aspects of temporal organization (i.e., the vowel-coda trading relationship) within the rhyme.