English |r|-|l| category assimilation by Japanese adults: Individual differences and the link to identification accuracy

Native speakers of Japanese often have difficulty identifying English /r/ and /l/, and it has been thought that second-language (L2) learning difficulties like this are caused by how L2 phonemes are assimilated into ones native phonological system. This study took an individual difference approach to examining this relationship by testing the category assimilation of Japanese speakers with a wide range of English /r/-/l/ identification abilities. All Japanese subjects were assessed in terms of (1) their accuracy in identifying English /r/ and /l/, (2) their assimilation of /r/ and /l/ into their Japanese flap category, (3) their production of /r/ and /l/, and (4) their best-exemplar locations for /r/, /l/, and Japanese flap in a five-dimensional set of synthetic stimuli (F1, F2, F3, closure duration, and transition duration). The results demonstrated that Japanese speakers assimilate /l/ into their flap category more strongly than they assimilate /r/. However, there was little evidence that category assimilation was predictive of English /r/-/l/ perception and production. Japanese speakers had three distinct best exemplars for /r/, /l/, and flap, and only their representation of F3 in /r/ and /l/ was predictive of identification ability.