The Differential Role of Executive Functions in the Cognitive Control of Language Switching

The effect of inhibitory control and language proficiency on intra-sentential switching costs in reading comprehension

Based on the inhibition account and activation account, inhibitory control and language proficiency play big roles on language control mechanisms underlying language switching respectively. But it is still debatable whether inhibitory control and language proficiency play roles in sentential context during bilingual language comprehension, and how and when they work if they both do. The present study examined the specific roles of language proficiency and inhibitory control on modulating intra-sentential switching costs in Chinese-English bilinguals using self-paced reading task. Results indicated that language proficiency and switching direction modulated intra-sentential switching costs significantly. Switching costs were larger when switching into L1 than into L2 for the first two code-switched words due to inhibitory effect, but more costly switching into L2 than into L1 since the third code-switched words owing to the effect of relative language proficiency. During bilingual language processing, inhibition and activation of languages shaped a dynamic interplay of complementary language control processes. Specifically, inhibitory control and language proficiency work as a dynamic continuum in language switching at sentence level. Switching into L1 requires the release of inhibition to L1, but switching into L2 asks the activation and access of L2. The interaction effects of language proficiency and inhibitory control influenced the exertion and components of inhibition. This study reconciled the independent roles of language proficiency and inhibitory control on language switching and constructed a new continuum based on language proficiency.

Uncovering the effects of bilingual language control on rational decisions: An ERP study

A growing body of research suggests that the language in which bilinguals make decisions affects the rationality of such decisions. Furthermore, bilinguals constantly confront cross-language interference that requires complex language control processes to resolve this competition. However, the relationship between language control and decision-making is unclear. In the current study, we analyze electrophysiological and behavior data elicited from two groups of Chinese-English bilinguals. One group was trained in intensive language switching and then completed the Iowa Gambling Task (IGT) and the other group completed the two tasks in the reverse order. We found that bilinguals who first received language switching training significantly scored higher on the IGT, with the score positively correlating with L1 and L2 switch costs. More importantly, training with language switching first led to an N2 component for L1 switching costs that negatively correlated with both loss feedback-related negativity and the P3 component. These effects did not emerge among the group of bilinguals who performed the IGT first. Taken together, the findings suggest that bilinguals are assisted in making rational decisions by language control on feedback evaluation.

Second Language Proficiency Modulates the Dependency of Bilingual Language Control on Domain-General Cognitive Control

The relationship between bilingual language control and domain-general cognitive control has been a hot topic in the research field of bilingualism. Previous studies mostly examined the correlation between performances of bilinguals in language control tasks and that in domain-general cognitive control tasks and came to the conclusions that they overlap, partially overlap, or are qualitatively different. These contradictory conclusions are possibly due to the neglect of the moderating effect of second language (L2) proficiency, that is, the relationship between bilingual language control and domain-general cognitive control might vary with the L2 proficiency of bilinguals. To examine this hypothesis, we recruited 36 unbalanced Chinese-English bilinguals to perform the Simon task (to assess domain-general cognitive control), Oxford Placement Test (to assess L2 proficiency), and picture naming tasks in single-and dual-language contexts (to evoke local and global language control). We find that Simon scores positively predicted switching costs in bilinguals with low L2 proficiency, but not in bilinguals with high L2 proficiency. Furthermore, Simon scores positively predicted mixing costs in bilinguals with high L2 proficiency, but not in bilinguals with low L2 proficiency. These results verify the moderating effect of L2 proficiency on the relationship between bilingual language control and domain-general cognitive control, that is, bilinguals with more proficient L2 rely on domain-general cognitive control less for local language control and more for global language control. This may imply a shift from local to global for the dependency of bilingual language control on domain-general cognitive control during the L2 development of bilinguals.

On the Connection Between Language Control and Executive Control-An ERP Study

Models vary in the extent to which language control processes are domain general. Those that posit that language control is at least partially domain general insist on an overlap between language control and executive control at the goal level. To further probe whether or not language control is domain general, we conducted the first event-related potential (ERP) study that directly compares language-switch costs, as an index of language control, and task-switch costs, as an index of executive control. The language switching and task switching methodologies were identical, except that the former required switching between languages (English or Spanish) whereas the latter required switching between tasks (color naming or category naming). This design allowed us to directly compare control processes at the goal level (cue-locked ERPs) and at the task performance level (picture-locked ERPs). We found no significant differences in the switch-related cue-locked and picture-locked ERP patterns across the language and task switching paradigms. These results support models of domain-general language control.

Switching between newly learned languages impacts executive control

Previous research has explored the relationship between language control and executive control based on performance in bilinguals' skilled languages. However, this relationship between bilingualism and executive control has not been examined at the very initial stage of language learning. In the present study, we trained Chinese speakers to learn words in German and Japanese, two languages with which they had no prior experience. In pre- and post-training, we measured participants' electrophysiological data to investigate how switching between these two newly learned languages affected executive control. We observed that, while lacking the language switching effect in the behavioral data, a flanker task elicited larger N2 and P3 amplitudes in the post-training session when participants were required to switch between German and Japanese compared to when they responded to only German or Japanese. These results provided evidence of language control of newly learned languages on domain-general executive control, specifically at the (very) initial period of language learning. Our findings support the adaptive nature of the relationship between bilingual language control and executive control.