Differential adaptation of bilingual language control to cognitive load: Evidence from cued and voluntary switching

Bilingual speakers must regulate cross-language competition to communicate effectively, yet this regulation typically unfolds under concurrent cognitive demands. To characterise how cognitive load shapes bilingual control, we used a dual-task picture-naming paradigm in which 78 proficient Chinese-English bilinguals performed single-language, cued-switching, and voluntary-switching blocks with and without a secondary tone-monitoring task. Cognitive load did not simply undermine performance; instead, it constrained control engagement and prompted context-sensitive reconfiguration. In cued switching, where the L2 is externally required and especially vulnerable to L1 interference, load shifted control towards a more proactive state that protected L2 access via global downregulation of the L1. In voluntary switching, where speakers can exploit trial-by-trial fluctuations in relative activation, load strengthened a reactive selection strategy: participants selected the L2 when it was rapidly accessible but fell back to the L1 when L2 activation was insufficient. Overall, bilingual control adapted to cognitive load by shifting both the mode and strategy of control in a context-dependent manner, showing that what adapts is not only the type of control recruited, but also how it is employed as contextual demands fluctuate.