Acoustic Similarity Predicts Vowel Phoneme Detection in an Unfamiliar Regional Accent: Evidence from Monolinguals, Bilinguals and Second-Language Learners

When encountering an unfamiliar accent, a hypothesized perceptual challenge is associating its phonetic realizations with the intended phonemic categories. Greater accumulated exposure to the language might afford richer representations of phonetic variants, thereby increasing the chance of detecting unfamiliar accent speakers’ intended phonemes. The present study examined the extent to which the detection of vowel phonemes spoken in an unfamiliar regional accent of English is facilitated or hindered depending on their acoustic similarity to vowels produced in a familiar accent. Monolinguals, experienced bilinguals and native German second-language (L2) learners completed a phoneme detection task. Based on duration and formant trajectory information, unfamiliar accent speakers’ vowels were classed as acoustically “similar” or “dissimilar” to counterpart phonemes in the familiar accent. All three participant groups were substantially less sensitive to the phonemic identities of “dissimilar” compared to “similar” vowels. Unlike monolinguals and bilinguals, L2 learners showed a response shift for “dissimilar” vowels, reflecting a cautious approach to these items. Monolinguals displayed somewhat heightened sensitivity compared to bilinguals, suggesting that greater accumulated exposure aided phoneme detection for both “similar” and “dissimilar” vowels. Overall, acoustic similarity predicted the relative success of detecting vowel phonemes in cross-dialectal speech perception across groups with varied linguistic backgrounds.