L1 category precision hypothesis in L2 production: Korean learners’ English front vowels

Abstract

It has been hypothesized that learners with more precisely defined categories in their native language (L1) are better at learning nonnative sounds in a second language (L2). Some perception studies have supported this hypothesis, but not many production studies have been conducted. Our study aims to fill this gap. Focusing on front vowels in F1/F2 acoustic space, we calculated compactness scores of L1 vowels and distances between learners’ and native speakers’ productions to operationalize category precision and L2 accuracy, respectively. Then, we examined whether learners with a lower compactness score would produce L2 vowels with a closer distance. The learners’ productions were taken from a corpus containing native Korean speakers’ reading and retelling of the North Wind and the Sun in Korean and English and comparable native English speakers’ productions from ALLSSTAR corpus. Results showed that learners with lower compactness scores produced more accurate English /i/ and /ɪ/, but not for /ɛ/ or /æ/, which partially supports the hypothesis's application to L2 production. We speculate that the merger between /e/ and /æ/ in Korean, the Northern Cities Vowel Shift in English, and/or perceptual mapping between native and L2 categories are responsible for the English non-high vowel results.