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Description: Bilinguals often outperform monolinguals in nonverbal tasks of cognitive control. For example, a meta-analysis of studies that compared the performance of bilinguals and monolinguals on conflict resolution tasks (e.g., the Stroop task) revealed a moderately significant bilingual advantage (Donnelly, Brooks, & Homer, 2015). At first blush, this finding augments our understanding of far transfer effects (how practice in one domain [language] results in changes to other [non-language] domains) and may inform educational policies and social practice. However, close inspection of the empirical data yield inconclusive results. For example, the effect reported in the above meta-analysis appears to be driven by data from a single study. Furthermore, the meta-analysis also revealed a large and significant main effect of ‘lab’ (research group). The inconsistent results, combined with publication bias (de Bruin, Treccani, & Della Sala, 2015), has led many scientists (e.g., Duñabeitia & Carreiras, 2015; Klein, 2016; Paap, Johnson, & Sawi, 2016) to question whether the bilingual advantage is real or merely an artefact of particular research practices. Moreover, significant bilingual advantages have not been observed in studies with large sample sizes (see Paap, Johnson, & Sawi, 2016, for discussion). To progress beyond the controversy and advance the science, in addition to carrying out more studies, we must come up with a theory that can account for the inconsistencies in the literature and explain when, how, and why learning two or more languages improve cognitive control. This is the focus of the current project.