Language switching in picture naming: What asymmetric switch costs (do not) tell us about inhibition in bilingual speech planning

Meuter and Allport (1999) were among the first to implicate an inhibitory mechanism in bilingual language control. In their study, bilinguals took longer to name a number in the L1 directly following an L2 naming trial than to name a number in the L2 following an L1 naming trial, suggesting that bilinguals suppress the more dominant L1 during L2 production. Since then, asymmetric switch costs have not been replicated in all subsequent studies, and some have questioned whether switch costs necessarily reveal language inhibition. Based on methodological grounds and interpretability problems, we conclude that switch costs may not be the most reliable index of inhibition in bilingual language control. We review alternative proposals for the source of switch costs, and point to other indices of inhibition within the switching paradigm and from adapted paradigms.