Age effects on late bilingualism: The production development of /ɹ/ by high-proficiency Japanese learners of English

The current project examined whether and to what degree age of acquisition (AOA), defined as the first intensive exposure to the target language, can be predictive of second language production attainment and nativelikeness of word-initial /ɹ/ by late English-Japanese bilinguals. Productions of /ɹ/ were elicited from 88 high-proficiency Japanese learners of English and comparison groups of 10 native English speakers and 10 low-proficiency Japanese learners of English. Tokens from word reading, sentence reading, and timed picture description tasks were assessed through listener judgements and acoustic analyses. The results demonstrated that AOA significantly predicted the attained performance of /ɹ/ at a spontaneous (picture description) but not a controlled (word and sentence reading) speech level, and with respect to third formant frequencies as determined by labial, palatal, and pharyngeal constrictions. In contrast, most Japanese learners exhibited ceiling effects regardless of AOA profiles with respect to second formant frequencies and transitional duration of first formants as determined by the degree and rate of tongue retraction. The results suggest that, whereas AOA continues to be a driving factor in the degree to which late bilinguals can benefit from additional input and interaction, such age effects may depend on different levels of phonetic processing.