Bilinguals often outperform monolinguals on executive function tasks, including tasks that tap cognitive flexibility, conflict monitoring, and task-switching abilities. Some have suggested that bilinguals also have greater working memory capacity than comparable monolinguals, but evidence for this suggestion is mixed. We therefore conducted a comprehensive meta-analysis on the effects of bilingualism on working memory capacity. Results from 88 effect sizes, 27 independent studies, and 2,901 participants revealed a significant small to medium population effect size of 0.20 in favor of greater working memory capacity for bilinguals than monolinguals. This suggests that experience managing two languages that compete for selection results in greater working memory capacity over time. Moderator analyses revealed that largest effects were observed in children than other age groups. Furthermore, whether the task was performed in the first (L1) or second (L2) language for bilinguals moderated the effect size of the bilingual advantage; this factor is often overlooked and our results point to the importance of defining language variables that influence critical cognitive outcomes.

What is the relationship between bilingual language control (BLC) mechanisms and domain-general executive control (EC) processes? Do these two domains share some of their mechanisms? Here, we take a novel approach to this question, investigating whether short-term language switching training improves non-linguistic task switching performance. Two groups of bilinguals were assigned to two different protocols; one group was trained in language switching (switching-task training group) another group was trained in blocked language picture naming (single-block training group). Both groups performed a non-linguistic and linguistic switching task before (pre-training) and after training (post-training). Non-linguistic and linguistic switch costs decreased to a greater extent for the switching-task training than for the single-block training group from pre- to post-training. In contrast, mixing costs showed similar reductions for both groups. This suggests short-term language switching training can transfer to the non-linguistic domain for certain sub-mechanisms (i.e., switch cost). Thus, there is some overlap of the control mechanisms across domains.

How flexible is bilingual language control and how does it adapt to the linguistic context of a conversation? We address this by looking at the pattern of switch costs in contexts involving mostly the use of a dominant or non-dominant language. This linguistic context affected switching patterns: switching was equally costly for both languages in a dominant (L1) context, while switching was harder for the weaker language in the non-dominant (L2) context. Also, naming latencies for each language were affected by the linguistic contexts: only the dominant L1 context led to slower latencies for the dominant language. This latter finding was also present when looking at the LPC component, which may reveal differences in the way inhibitory control is applied depending on the linguistic context. These results reveal that the bilingual language control system is flexible and that it adapts to the linguistic context in which the speaker is placed.

How do faces with social-cultural identity affect bilingual language control? We approach this question by looking at the switch cost patterns and reversed language dominance effect, which are suggested to reflect bilingual language control mechanisms, in the absence (i.e., baseline context) or presence of faces with socio-cultural identity (Asian or Caucasian). In separate blocks, the face matched (i.e., congruent context) or mismatched (i.e., incongruent context) the language to be spoken. In addition, cue preparation time was manipulated to be long (Experiment 1) or short (Experiment 2). In both experiments, a unique asymmetric switch cost with larger costs for L2 was observed in the congruent context as compared with the baseline and incongruent contexts. Furthermore, the reversed language dominance effect was not modulated across contexts. These results suggest a critical role of contextual faces in modulating local but not global language control. Thus, bilingual language control changes flexibly within an environment that includes faces with socio-cultural identity.

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