This is quite a study by Gunnured et al. It checks a lot of quality boxes, such as preregistration, open data…
The topic is a field that has been quite difficult to examine, as it discusses the influence of bilingualism on executive functions (EF) of children. Why is this kind of research difficult? Well, while EF is a hot topic, there is still not really an agreement about the components of EF. Also the past few years the field of studies on the advantages of bilingualism has been a bit of a battlefield with mixed results in replication studies.
The results in short:
The hypothesis that bilingual children have a cognitive advantage related to their executive function has been accepted as a truth in both society and research. However, the present meta-analysis, which is based on a large number of studies (143 comparisons and 583 effect sizes), gives little compelling support for the position that a bilingual advantage exists for overall executive function. Importantly, there was large heterogeneity in results and studies of middle-class children and studies using switching tasks, and studies from one lab demonstrated larger effects.
The researchers did find a significant but small effect on average, but they mention a clear publication bias, and that last element with one lab being a good predictor for larger effects is quite awkward. That the benefits can be found in children from middle-class and not for children from both low or upper-class families is important, but the researchers also note that:
Overall, more studies were present with middle-class children, but only a few were conducted with those of the low or upper-middle class.
This is an element of the discussion that will probably stir some… ehm, discussion:
Although the overall mean effect size was rather small, true variation was identified between studies, which may suggest that a bilingual advantage might be present under certain conditions or circumstances. The results indicated a significant effect for samples with middle-class SES bilinguals, wherein samples with those with a middle SES had a bilingual advantage, and those with a low SES and upper-middle SES had no bilingual advantage. This conflicts with suggestions that bilingualism can work as an enrichment for bilingual children of low SES.
I do agree with the researchers that this warrants more research, as…
…it might very well be third variables underlying this relationship (i.e., that the sample of studies with middle-class children have something else in common that is driving the effect). It is also important to note that the SES variable here mainly consists of studies having measured parental education. This is a rather crude SES measure, and in some cases, parents may have low education but high income.
Now what is the final conclusion?
Thus, overall, our findings align with the conclusion in the narrative review from Paap et al. (2015) that “bilingual advantages in executive functioning either do not exist or are restricted to very specific and undetermined circumstances” (p. 265). The circumstances in which this conclusion prevailed in this study were related to middle-class SES, to one lab, and to switching tasks. Still, the main advantage of being bilingual may merely be one’s ability to master two or more languages, which may, nevertheless, afford numerous alternative advantages, such as the opportunity to become familiar with various cultures, keep in contact with relatives, increase one’s competitiveness in employment, and open up new social opportunities.
Abstract of the study:
Bilingual people are often claimed to have an advantage over monolingual people in cognitive processing owing to their ability to learn and use two languages. This advantage is considered to be related to executive function (EF). However, no consensus exists as to whether this advantage is present in the population or under which conditions it prevails. The present meta-analysis examines the bilingual advantage in EF of children aged 18 years and under for different components of inhibition (hot; rewarding stimuli/cold; neutral stimuli), attention, switching, monitoring, working memory, and planning in 143 independent group comparisons comprising 583 EF effect sizes. The bilingual advantage in overall EF was significant, albeit marginal (g = 0.06), and there were indications of publication bias. A moderator analysis showed significant group differences on EF in favor of bilinguals for studies of children from middle-class socioeconomic backgrounds and studies from one specific lab. The EF components of cold inhibition, switching, and monitoring expressed significant bilingual advantages, but monitoring and cold inhibition were affected by publication bias. As for switching, this remained significant after controlling for publication bias. Thus, given the small mean effect size and small-study effects, this meta-analysis gives little support for a bilingual advantage on overall EF. Still, also after the moderator analysis, there was a large heterogeneity of true effects and a large amount of unexplained heterogeneity in the effect sizes. Thus, there might be bilingual advantages (or disadvantages) under conditions that this study is not able to identify through the analysis of 12 moderators.