Emotional states change the behavioral meaning of interbrain synchronization in dyadic bilingual language control.

Bilingual conversation requires coordination between a speaker who selects and produces the target language and a listener who monitors and responds to that output. The present study examined whether emotional state moderates the association between interbrain synchronization and behavioral performance during a controlled dyadic bilingual task. Sixty-two Chinese-English bilinguals formed 31 proficiency-matched dyads. One partner named pictures in Chinese or English, whereas the other made animacy judgments on the producer's spoken responses. Dyads completed mixed- and single-language blocks under experimentally induced negative, neutral, and positive emotional states while dual-EEG was recorded. Behaviorally, both negative and positive states were associated with faster overall responses than the neutral state in production and comprehension. Both states also reduced mixing costs in production, whereas the corresponding comprehension effects were more restricted. Critically, the association between interbrain phase-locking value (PLV) and reaction time differed across emotional states. Under neutral emotion, stronger PLV was often associated with slower responses. Several corresponding associations were more negative under the negative condition, with the clearest negative-neutral difference observed for producer alpha-band PLV. The positive condition produced a more heterogeneous pattern across interlocutor roles, frequency bands, and task contrasts. These findings indicate that PLV-behavior associations during bilingual interaction are not uniform across emotional states. These findings show that emotional context moderates how cross-brain phase consistency covaries with bilingual performance.