Phonetic interaction between late Japanese-English bilinguals' L1 and L2 vowels—A longitudinal study

We investigated late bilinguals' (N = 31) change in their production and perception of the L1 Japanese vowel /i/ and its phonetically associated L2 vowel /i/ and /I/ over one year. The perceptual boundaries between both English /i/-/I/ and Japanese /i/-/e/ were examined through identification tasks. Participants' production of the high front vowels was also analyzed. More than half of the participants exhibited evidence of separating English and Japanese high front vowels from each other in production. Participants who seemed to use similar F1-F2 values for these vowels still tended to separate them. The perception task results showed a perceptual boundary shift in bilinguals' L1 Japanese after one year. That is, they identified more tokens as /i/ than /e/ in /i/-/e/ continuum. This phenomenon was also observed when comparing bilinguals to Japanese monolingual controls. We argue that this change in L1 perception stems from learning a new L2 phonetic category /I/ and associating it with a similar L1 /i/. Individual differences in bilinguals' relative language use and exposure were also examined as potential factors driving changes in perception and production of Japanese/English high front vowels.