Vowel compensation under formant perturbation: A cross-linguistic comparison of Japanese, Chinese, and Vietnamese

This study examines how native languages influence auditory–speech motor control of vowel production. Sensory feedback is crucial for speech adaptation. Formant-altered auditory feedback (AAF) experiments, which apply frequency perturbations to vowels, observe speaker compensation. Previous research, however, lacked sufficient validation across multiple non-English L1s with consistent perturbation conditions. To address this, we conducted a formant AAF experiment with native speakers of Japanese, Chinese, and Vietnamese. Participants (10 per language group) produced native /e/ and English /e/. The experiment utilized F1-Increase and F1-Decrease AAF conditions, perturbing F1 frequency by up to ±200 Hz. F1 adaptation, calculated from the Hold phase (trials 71–90) where perturbation was constant, represented compensatory responses. Characteristic compensation patterns emerged: Japanese speakers adapted more to F1-Decrease; Chinese speakers to F1-Increase; Vietnamese speakers showed similar adaptation. Significant cross-linguistic differences appeared for English /e/ adaptation under the Increase condition. The “Influence” index, which quantifies how a language’s F1–F2 vowel distribution aligns with the direction of perturbation (specifically, how native vowels are distributed relative to the perturbed vowel and the perturbation vector), closely mirrored these compensation tendencies. These findings suggest that the structure of native language vowel systems significantly shapes auditory–speech motor control.