Perceived Phonological Overlap in Second-Language Categories: The Acquisition of English /r/ and /l/ by Japanese Native Listeners

Japanese learners of English can acquire /r/ and /l/, but discrimination accuracy rarely reaches native speaker levels. How do L2 learners develop phonological categories to acquire a vocabulary when they cannot reliably tell them apart? This study aimed to test the possibility that learners establish new L2 categories but perceive phonological overlap between them when they perceive an L2 phone. That is, they perceive it to be an instance of more than one of their L2 phonological categories. If so, improvements in discrimination accuracy with L2 experience should correspond to a reduction in overlap. Japanese native speakers differing in English L2 immersion, and native English speakers, completed a forced category goodness rating task, where they rated the goodness of fit of an auditory stimulus to an English phonological category label. The auditory stimuli were 10 steps of a synthetic /r/–/l/ continuum, plus /w/ and /j/, and the category labels were L, R, W, and Y. Less experienced Japanese participants rated steps at the /l/-end of the continuum as equally good versions of /l/ and /r/, but steps at the /r/-end were rated as better versions of /r/ than /l/. For those with more than 2 years of immersion, there was a separation of goodness ratings at both ends of the continuum, but the separation was smaller than it was for the native English speakers. Thus, L2 listeners appear to perceive a phonological overlap between /r/ and /l/. Their performance on the task also accounted for their responses on /r/–/l/ identification and AXB discrimination tasks. As perceived phonological overlap appears to improve with immersion experience, assessing category overlap may be useful for tracking L2 phonological development.