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

Abstract

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 (BF 10 = 2.91 9 10 8 ), 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.

Bilingual speakers’ enhanced monitoring can slow them down

“…Speaking another language leads to changes in brain structure and function, particularly in the networks implicated in cognitive control (Li et al, 2014; Pliatsikas & Luk, 2016). Consequently, differences have been found between monolingual and bilingual speakers in tasks of executive control, with many studies finding superior behavioural performance for bilinguals (Bialystok et al, 2004; Costa et al, 2008; Emmorey et al, 2008; Hernández et al, 2010; review in Bialystok et al, 2012; meta-analyses in Donnelly et al, 2019; Grundy, 2020). However, other studies have found similar performance in the two participant groups or even superior performance in monolinguals (Duñabeitia et al, 2014; Gathercole et al, 2014; Naeem et al, 2018; Paap et al, 2015; review in Nichols et al, 2020; meta-analysis in Lehtonen et al, 2018).…”

Neural differences in the temporal cascade of reactive and proactive control for bilinguals and monolinguals

“…Future research should use a non‐word‐specific task with a similar design to investigate this further. Another important limitation to note is that not all bilinguals are created equal, particularly when examining executive function differences (see Grundy, 2020 for a review). Factors such as specific language spoken, age of acquisition, and proficiency can skew the findings.…”

Clear Theories Are Needed to Interpret Differences: Perspectives on the Bilingual Advantage Debate

“…A more comprehensive overview of the literature on this topic has been provided in recent systematic reviews (e.g., Antoniou, 2019;Bialystok, 2017;Van den Noort, Struys, & Bosch, 2019) and meta-analyses (e.g., Donnelly et al, 2019;Grundy, 2020;Gunnerud et al, 2020;Lehtonen et al, 2018;Paap, 2019). While there is both evidence for and against a bilingual cognitive advantage, recent meta-analyses taking into account publication bias (e.g., Lehtonen et al, 2018) conclude that there is no strong or consistent evidence for enhanced executive functioning in bilinguals.…”

“…In addition, it is frequently claimed that differences may not be captured in young adults because they perform at ceiling, but that cognitive development and decline should allow for effects of bilingualism to occur in children and older adults (e.g., Kroll & Bialystok, 2013;Grundy, 2020). Meta-analyses, however, have found comparable (null) results in different age groups (e.g., younger and older adults, Lehtonen et al, 2018;children and young adults, Donnelly et al, 2019), suggesting that evidence for a bilingual advantage is not only limited in young adults, but also in children and (healthy) older adults.…”