Factors affecting word learning in second language acquisition

Three levels of mental representations are involved in lexical processing and acquisition: semantic (meaning), lexical (phonological sequence as a whole unit), and phonological (individual sounds and sound sequences). Studies of first language (L1) acquisition suggest that there is an interaction between phonological and lexical representations in word learning. Additional factors need to be considered in second language (L2) word learning, such as the L2-L1 phonological mapping and the L2 learners' language experience. The purpose of the current study was to explore how L2-L1 phonological mapping and experiential information impact L2 word learning for native speakers of Japanese learning English as an L2. Phonological representations were explored by examining the learner's perceptual knowledge of L2 sounds through a perceptual discrimination task (Same-Different Task), based on assimilation patterns of L2 sounds to L1 categories in the Perceptual Assimilation Model (PAM; Best, 1995). Productive knowledge was evaluated through a production probe containing English real words and nonwords. In exploring lexical representations, L2 word learning was examined through exposure to novel words and tested by two measures, referent identification and picture naming. Finally, information on L2 speakers' language experience was collected to examine whether any individual or combination of phonological and/or experiential variables predicted L2 word learning. The results of the Same-Different Task showed that IN-IN (two category assimilation) sound contrasts were discriminated more accurately than IN-OUT (categorized vs. uncategorizable), and OUT-OUT (both uncategorizable) sound contrasts, as predicted by PAM. For the production probe, IN sounds were produced more accurately than OUT sounds in both real words and nonwords, with more substitution errors observed for OUT sounds in nonwords than OUT sounds in real words. For L2 word learning, novel words composed of IN sounds were learned better than those composed of OUT sounds, suggesting that L2 phonological knowledge influences L2 word learning. In addition, perceptual variables predicted learning of OUT words, whereas a combination of phonological and experiential variables predicted learning of IN sounds. These results suggest that L2-L1 phonological mapping influences learning of L2 novel words consisting of OUT sounds.