Lexically-guided perceptual recalibration from acoustically unambiguous input in second language learners

• Unambiguous vowel substitutions trigger perceptual shifts in advanced L2 learners. • For an easy L2 contrast, learners show canonical perceptual recalibration effects. • Recalibration for the easy contrast generalizes across talkers with similar acoustics. • Unexpected shift that does not generalize across talkers for a difficult L2 contrast. • Exposure to variable word productions may affect the categorization of difficult L2 sounds. The present study investigated whether advanced late second-language (L2) learners adapt their perceptual categorization in response to categorical segmental substitutions in L2 words, and whether this differs depending on the difficulty of the targeted phonological contrast. In three experiments, German learners of English categorized acoustic continua for a contrast that also exists in their L1 (/i/-/ɪ/), and one that does not and is known to be challenging for them (/ɛ/-/æ/). Crucially, they did so after listening to sets of English words that were either all canonically produced or contained items with /ɪ/ → [i] and /æ/ → [ɛ] substitutions. Experiment 1 used the same male talker for exposure and test, Experiment 2 another male test talker with similar acoustics and Experiment 3 a female test talker. Results showed perceptual recalibration effects in the expected direction for /i/-/ɪ/ in Experiments 1 and 2, and a shift in the opposite direction for /ɛ/-/æ/ only in Experiment 1. This study extends previous findings to a non-native population and to vowel distinctions, provides novel insights on the cross-talker generalizability of perceptual recalibration effects and, importantly, highlights the need for more research investigating perceptual adaptation processes involving difficult non-native contrasts.