Voice onset time in Arabic L1 learners of English and Spanish: evidence for stability, interaction, and phonetic drift in multilingual speech

This study examines voice onset time (VOT) in Arabic first-language speakers learning English and Spanish as a multilingual test of the speech learning model-revised (SLM-r). The model predicts continuous phonetic learning, interaction among categories in a shared phonetic space, and bidirectional influence across languages. VOT production was examined in Arabic monolinguals, an Arabic–English bilingual group, an Arabic–English–Spanish multilingual group, and monolingual speakers of English and Spanish using a controlled reading task. Mixed-effects models incorporated group, phonetic condition, and continuous measures of proficiency and relative dominance. English aspirated /p/ was robustly differentiated from English /p/ after /s/ across groups, with a 57.21 ms model-estimated contrast. Spanish /p/ remained in the short-lag range and did not differ reliably between the multilingual group ( M = 15.10 ms) and Spanish monolinguals ( M = 14.17 ms). For voiced stops, Arabic monolinguals showed substantially more negative Arabic /b/ VOT ( M = −85.55 ms) than the Arabic-English ( M = −44.08 ms) and Arabic–English–Spanish ( M = −43.85 ms) groups, indicating reduced prevoicing in the Arabic L1 learner groups. English /b/ and Spanish /b/ also showed higher prevoicing among Arabic L1 learners than among the respective monolingual controls. Relative English–Spanish dominance did not reliably predict voiceless-stop VOT within the multilingual group. The findings support SLM-r claims about lifelong phonetic plasticity and selective cross-language interaction, while also suggesting that Spanish /p/ may reflect facilitative transfer from Arabic short-lag timing as well as stable category separation.