Phonetic alignment in English as a lingua franca: Coming together while splitting apart

This study investigates the plasticity of phonological boundaries during discourse in a lingua franca. We tracked the production of 34 Spanish learners of English conversing with two Dutch confederates in English across two speech styles, focusing on incremental changes in two key English vowel contrasts with differential effects of cross-linguistic influence (/i/–/？/ and /ε/–/？/). Results indicate that Spaniards align with Dutch confederates, quickly merging /ε/ and /？/ and gradually separating their merged /i/–/？/ category, rather than adopting native-like English production. We found greater merger in informal speech overall. We also found an interaction with time for the /i/–/？/ contrast, indicating that the merged /i/ and /？/ categories gradually separate in informal speech; this effect was not found for /ε/–/？/. Finally, proficiency modulates alignment: the most proficient speakers separate /i/–/？/ and merge /ε/–/？/ more than other speakers. We interpret phonetic alignment as a complex, dynamic phenomenon influenced by proficiency in discourse language and speaking style, and whose effects may unfold rapidly or gradually depending on the phonological category investigated