Inhibitory control training reveals a common neurofunctional basis for generic executive functions and language switching in bilinguals

Cognitive and neural mechanisms of voluntary versus forced language switching in Chinese-English bilinguals: an fMRI study

The ecological validity of bilingual code-switching has garnered increasing attention in recent years. Contrary to traditional studies that have focused on forced language switching, emerging theories posit that voluntary switching may not incur such a cost. To test these claims and understand differences between forced and voluntary switching, the present study conducted a systematic comparison through both behavioral and neural perspectives. Utilizing fMRI alongside picture-naming tasks, our findings diverge from prior work. Voluntary language switching not only demonstrated switching costs at the behavioral level but also significantly activated brain regions associated with inhibitory control. Direct comparisons of voluntary and forced language switching revealed no significant behavioral differences in switching costs, and both shared several common brain regions that were activated. On the other hand, a nuanced difference between the two types of language switching was revealed by whole-brain analysis: voluntary switching engaged fewer language control regions than forced switching. These findings offer a comprehensive view of the neural and behavioral dynamics involved in bilingual language switching, challenging prior claims that voluntary switching imposes no behavioral or neural costs, and thus providing behavioral and neuroimaging evidence for the involvement of inhibitory control in voluntary language switching.

Inhibitory control of the dominant language: Reversed language dominance is the tip of the iceberg

Theories of speech production have proposed that in contexts where multiple languages are produced, bilinguals inhibit the dominant language with the goal of making both languages equally accessible. This process often overshoots this goal, leading to a surprising pattern: better performance in the nondominant vs. dominant language, or reversed language dominance effects. However, the reliability of this effect in single word production studies with cued language switches has been challenged by a recent meta-analysis. Correcting for errors in this analysis, we find that dominance effects are reliably reduced and reversed during language mixing. Reversed dominance has also consistently been reported in the production of connected speech elicited by reading aloud of mixed language paragraphs. When switching, bilinguals produced translation-equivalent intrusion errors (e.g., saying pero instead of but) more often when intending to produce words in the dominant language. We show this dominant language vulnerability is not exclusive to switching out of the nondominant language and extends to non-switch words, linking connected speech results to patterns first reported in single word studies. Reversed language dominance is a robust phenomenon that reflects the tip of the iceberg of inhibitory control of the dominant language in bilingual language production.

Executive Functions and Foreign Language Learning

Executive functions (EFs) serve as an umbrella term to describe a set of higher-order cognitive abilities that include working memory, inhibitory control, cognitive flexibility, planning, reasoning, and problem-solving. Various studies suggest that foreign language learning likely promotes executive functions, but others suggest that executive functions could improve foreign language learning. The aim of this study is to investigate the relationship between executive functions and foreign language learning and how these processes could interact. The sample included 64 children from kindergarten, aged 4-5 years, with no documented neuropsychiatric disorders, and from the middle-high literacy group. They were divided into three groups based on the level of their knowledge of the foreign language. A significant effect of the group on the executive tasks is shown in the comparison of the groups. Children who belonged to a group that had advanced foreign language proficiency had better results in executive tasks. Our results suggest that the higher the level of foreign language proficiency, the higher the performance of the executive tasks. However, we do not know if there is a causal effect between these variables.