A longitudinal study of English and Japanese vowel production by Japanese adults and children in an English immersion setting.

The effect of age of acquisition on first‐ and second‐language vowel production was investigated. Eight English vowels were produced three times in two different words each by 16 native Japanese (NJ) adults and children as well as 16 age‐matched native English (NE) speaking adults. Productions were recorded shortly after the NJ participants’ arrival in the United States and then 1 year later. In agreement with previous investigations [Aoyama et al., J. Phonetics 32, 233–250 (2004)], children were able to learn faster, leading to higher accuracy than adults in a year’s time. Based on acoustic measurements, NJ adults had more accurate production at Time 1 but made no changes across time. The NJ children, on the other hand, showed significant differences from NE children’s productions for /ɪ/, /e/, /ɑ/, /ʌ/, and /U/ at Time 1, but produced all eight vowels in a native‐like manner at Time 2. A follow up examination of NJ children’s productions of Japanese /i/, /a/, /u/ revealed significant changes for Japanes...