General adaptation to accented English: Speech intelligibility unaffected by perceived source of non-native accent.

Foreign-accented speech commonly incurs a processing cost, but this cost can be offset when listeners are given informative cues to the speaker's purported ethnicity and/or language background. This study investigates the mechanism that underlies this facilitatory effect of top-down expectation, evaluating between general adaptation (an across-the-board relaxation of phonetic categorization criteria) and targeted adaptation (tuning in to accent-specific phonetics). In experiment 1, native speakers of American English completed a transcription-in-noise task with Chinese-accented English sentences. All listeners heard the same voice but were randomly assigned to one of four visual conditions: a blank silhouette, a European face, an East Asian face, or a South Asian face. Results showed that although there was no significant effect of visual condition, listeners who believed the speaker to be non-natively accented enjoyed significantly improved performance compared to those who reported hearing a native accent. Crucially, however, listeners who correctly perceived the speaker as Chinese-accented showed no additional benefit over those who heard some other foreign accent. This basic pattern held even when listeners were primed to expect congruent face-accent pairings (experiment 2). Overall, these results provide evidence for a general adaptation mechanism, rather than a targeted mechanism involving accent-specific phonetic adjustments.