Cross-linguistic transfer of acoustic cues: Perception of Japanese vowel length by learners from Vietnamese-speaking background

This study examined how three groups of Vietnamese learners of Japanese perceive Japanese vowel length, focusing on duration and pitch cues. Seventy-five Vietnamese participants across three proficiency levels (N1, N2, N3) and 10 native Japanese (NJ) speakers completed a two-alternative forced-choice identification task using /kado/ and /kaado/ stimuli varying in duration and F0. Results showed that Vietnamese learners primarily relied on duration, similar to NJ speakers, but exhibited delayed categorical boundaries. While their first language (L1) experience with contrastive duration in Vietnamese tense–lax vowels may enhance durational sensitivity, it does not fully resolve challenges in distinguishing Japanese contrasts. Despite L1 experience with lexical tones, Vietnamese learners struggled to use pitch as a secondary cue. This may result from L1 strategies, which primarily link duration to vowel quality for tense–lax vowel discrimination, rather than to pitch. Limited familiarity with Japanese pitch accent and second-language-specific strategies for vowel length may have further hindered Vietnamese learners from integrating pitch cues with duration for vowel length perception. Among the three learner groups, only advanced learners (N1) showed modest adaptation in integrating pitch with duration, whereas lower-proficiency groups (N2 and N3) relied almost exclusively on duration. These findings highlight the influence of L1 experience on second language (L2) perceptual strategies and the need for explicit phonetic training to help L2 learners develop native- like cue weighting.