Distributional Learning of L2 Phonological Categories by Listeners with Different Language Backgrounds

Learning a second language (L2) is a complex task that often takes years before functional communicative skills are attained, and that rarely results in native-like proficiency. One of the biggest challenges for an L2 learner is acquiring the sounds and sound patterns of a new language. Beginner learners struggle with both perception and production of novel sounds, and even years of practice do not generally erase a foreign accent.* In this paper we are concerned with the problem of acquiring a new sound system from the perspective of a naïve listener. Previous research in this area has shown that perception of novel sounds is largely affected by native language (L1) phonology. Specifically, L2 learners often have difficulty perceiving distinctions between L2 sounds that do not form separate speech categories in their L1: e.g., the English r-l contrast is hard for L1-Japanese listeners who only have one category fitting the same acoustic-phonetic space (Miyawaki et al. 1975). These difficulties have been explained as a result of L2 being processed through the L1-attuned perceptual filter (Kuhl and Iverson 1995, Trubetzkoy 1939/1969), which has generally been conceptualized as a process of mapping L2 sounds onto the representations of L1 sound categories that are acoustically or articulatorily most similar (Best 1995, Best and Tyler 2007, Flege 1995). In these theories (following the terminology introduced by Best and colleagues), discrimination of two L2 sounds is predicted to be easy if each sound maps, or assimilates, onto a different L1 category (two-category assimilation), or if at least one of the sounds is very distinct from any sound in the L1 inventory (nonassimilation). Discrimination is relatively impaired when two L2 sounds are perceived as imperfect exemplars of only one L1 category (category-goodness difference). Finally, discrimination is hard if two L2 sounds assimilate completely onto one L1 category (single-category assimilation).