Increased second‐language vocabulary size is associated with more consistent second‐language vowel categorization and better discrimination.

Abstract

Improvement in second‐language (L2) perception has been posited to asymptote early in L2 learning when the L2 vocabulary is still small, whereas a large L2 vocabulary curtails perceptual learning [PAM‐L2: Best and Tyler (2007)]. We extend this proposition by suggesting that early L2 lexical development facilitates establishment of phonological categories in a manner analogous to toddlers’ L1 acquisition before versus after the vocabulary explosion. According to this revised view, L2 speech should be assimilated more consistently to phonological categories, and cross‐boundary contrasts discriminated more accurately, by learners with large versus small L2 vocabularies. We applied a novel whole‐system approach to evaluate perception of L2 vowels with respect to the L1 vowel system. Japanese learners of Australian English with under 12 weeks of L2 immersion completed labeling and goodness ratings on all Australian vowels, using all mono‐ and bi‐moraic Japanese vowels and vowel combinations. They also completed discrimination tasks on four L2 vowel contrasts, representing a range of PAM‐L2 contrast types, and a L2 vocabulary size assessment. Learners with larger vocabularies had more consistent vowel assimilation and more accurate cross‐boundary discrimination than those with smaller vocabularies, supporting the proposition that lexical development supports L2 phonological acquisition. [Work supported by NIH and MARCS/UWS.]