The effects of bilingualism on executive functions: an updated quantitative analysis

Several researchers have suggested that learning and using a second language requires domain-general executive functions, and many have shown that bilinguals outperform monolinguals on tasks that tap into these processes. However, recent behavioral studies and meta-analyses reporting failed replications have called into question whether or not bilingualism leads to changes in domain-general executive functions. The present paper argues that there are several reasons, often overlooked, that lead to failed replications, and that when group differences do appear on EF tasks, despite these issues, performance favors bilinguals far more often than monolinguals. The present paper reports a Bayesian analysis of 167 independent studies to support this claim with a Bayes Factor classified as “decisive” evidence for the alternative (BF10 = 2.91 × 108), ruling out chance outcomes that would predict an equal number of studies favoring monolinguals to studies favoring bilinguals. These findings could not be explained by publication bias, year of publication, or sample size. Critically, these findings are not at odds with recent meta-analyses examining overall effect sizes, but rather, highlight the need to determine when, rather than if, bilinguals outperform monolinguals on EF tasks.