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This study examines relative weighting of two acoustic cues, vowel duration and spectra, in the perception of high front vowels by Japanese learners of English. Studies found that Japanese speakers rely heavily on duration to distinguish /i?/ and [character omitted] in American English (AmE) as influenced by phonemic length in Japanese /ii/ and /i/, while spectral cues are more important for native AmE speakers. However, little is known as to whether and how this non-native perceptual weighting can change as a result of L2 learning. By employing computational and experimental methods, the present study shows that Japanese learners of English exhibit different cue weighting depending on which language they think they hear. The experiment shows that listeners use more spectral cues and less durational cues when they think they are listening to 'English' stimuli as opposed to 'Japanese' stimuli, despite the stimuli being identical. This result is generally in line with our computer simulation, which predicts distinct developmental paths in first language (L1) and second language (L2) perception. The Second Language Linguistic Perception (L2LP) model, which incorporates the language mode hypothesis, provides a comprehensive explanation for the current findings.

This study investigates the predictions of second language (L2) speech acquisition models — SLM(-r), PAM(-L2), and L2LP — on how native (L1) Japanese speakers implement the spectral and temporal aspects of L2 American English vowel categories. Data were obtained from 102 L1 Japanese speakers in the J-AESOP corpus, which also includes nativelikeness judgments by trained phoneticians. Spectrally, speakers judged to be non-nativelike showed a strong influence from L1 categories, except L2 /ʌ/ which could be deflected away from L1 /a/ according to SLM(-r) and L2 /ɑː/ which seemed orthographically assimilated to L1 /o/ according to PAM(-L2). More nativelike speakers showed vowel spectra similar to those of native English speakers across all vowels, in accordance with L2LP. Temporally, although speakers tended to equate the phonetic length of English vowels with Japanese phonemic length distinctions, segment-level L1-L2 category similarity was not a significant predictor of the speakers' nativelikeness. Instead, the implementation of prosodic-level factors such as stress and phrase-final lengthening were better predictors. The results highlight the importance of suprasegmental factors in successful category learning and also reveal a weakness in current models of L2 speech acquisition, which focus primarily on the segmental level. Theoretical and pedagogical implications are discussed. [ABSTRACT FROM AUTHOR]