Corrigendum: The effects of executive functions on language control during Chinese-English emotional word code-switching

[This corrects the article DOI: 10.3389/fpsyg.2023.1087513.].

Genetic bases of language control in bilinguals: Evidence from an EEG study

Previous studies have debated whether the ability for bilinguals to mentally control their languages is a consequence of their experiences switching between languages or whether it is a specific, yet highly-adaptive, cognitive ability. The current study investigates how variations in the language-related gene FOXP2 and executive function-related genes COMT, BDNF, and Kibra/WWC1 affect bilingual language control during two phases of speech production, namely the language schema phase (i.e., the selection of one language or another) and lexical response phase (i.e., utterance of the target). Chinese-English bilinguals (N = 119) participated in a picture-naming task involving cued language switches. Statistical analyses showed that both genes significantly influenced language control on neural coding and behavioral performance. Specifically, FOXP2 rs1456031 showed a wide-ranging effect on language control, including RTs, F(2, 113) = 4.00, FDR p = .036, and neural coding across three-time phases (N2a: F(2, 113) = 4.96, FDR p = .014; N2b: F(2, 113) = 4.30, FDR p = .028, LPC: F(2, 113) = 2.82, FDR p = .060), while the COMT rs4818 (ts >2.69, FDR ps < .05), BDNF rs6265 (Fs >5.31, FDR ps < .05), and Kibra/WWC1 rs17070145 (ts > -3.29, FDR ps < .05) polymorphisms influenced two-time phases (N2a and N2b). Time-resolved correlation analyses revealed that the relationship between neural coding and cognitive performance is modulated by genetic variations in all four genes. In all, these findings suggest that bilingual language control is shaped by an individual's experience switching between languages and their inherent genome.

The effects of executive functions on language control during Chinese-English emotional word code-switching

Executive functions (EFs) have great impact on language control indexed by language switch costs during production-based language switching. Yet, how they influence language control during comprehension-based language switching between embodied first language (L1, Chinese) emotional words and less embodied second language (L2, English) emotional words is less understood. Employing an emotional priming paradigm, this study recruited Chinese-English bilinguals as participants, and used emotional faces and words as experimental materials to explore the effects of cool [i.e., inhibitory control ability, IC ability] and hot (i.e., emotional valence and emotional congruency) EFs on language switch costs (i.e., language control) during Chinese-English emotional word comprehension. The results showed larger language switch costs in the emotional congruent condition relative to emotional conflict condition, larger Chinese switch costs than English switch costs, and larger language switch costs for negative over positive emotional words in the emotional congruent condition. In addition, high-IC participants showed larger English switch costs for negative emotional words compared with low-IC participants. These results indicated that hot EF and the embodiment of language had an impact on both language control and the modulation of cool EF on language control, and that the components of hot EFs interacted and jointly affected language control during language switching.

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.

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.

Clustering and Switching in Verbal Fluency Across Varying Degrees of Cognitive Control Demands: Evidence From Healthy Bilinguals and Bilingual Patients With Aphasia

Different linguistic contexts place varying amounts of cognitive control on lexical retrieval in bilingual speakers, an issue that is complicated in bilingual patients with aphasia (BPWA) due to subsequent language and cognitive deficits. Verbal fluency tasks may offer insight into the interaction between executive and language control in healthy bilinguals and BPWA, by examining conditions with varying cognitive control demands. The present study examined switching and clustering in verbal fluency tasks in BPWA and healthy bilinguals across single- and dual-language conditions. We also examined the influence of language processing and language proficiency on switching and clustering performance across the dual-language conditions. Thirty-five Spanish-English BPWA and twenty-two Spanish-English healthy bilinguals completed a language use questionnaire, tests of language processing, and two verbal fluency tasks. The semantic category generation task included four conditions: two single-language conditions (No-Switch L1 and No-Switch L2) that required word production in each language separately; one dual-language condition that allowed switching between languages as desired (Self-Switch); and one dual-language condition that required switching between languages after each response (Forced-Switch). The letter fluency task required word production in single-language contexts. Overall, healthy bilinguals outperformed BPWA across all measures. Results indicate that switching is more sensitive to increased control demands than clustering, with this effect being more pronounced in BPWA, underscoring the interaction between semantic executive processes and language control in this group. Additionally, for BPWA switching performance relies on a combination of language abilities and language experience metrics.

Correction: Assessing the Evidence for Asymmetrical Switch Costs and Reversed Language Dominance Effects - A Meta-Analysis

This article details a correction to: Gade, M., Declerck, M., Philipp, A. M., Rey-Mermet, A., & Koch, I. (2021). Assessing the Evidence for Asymmetrical Switch Costs and Reversed Language Dominance Effects – A Meta-Analysis. Journal of Cognition, 4(1), 55. DOI: http://doi.org/10.5334/joc.186

Bilingual Language Control Flexibly Adapts to Cultural Context

How does bilingual language control adapt to the cultural context? We address this question by looking at the pattern of switch cost and reversed language dominance effect, which are suggested to separately reflect reactive and proactive language control mechanisms, in the contexts with culturally-neutral pictures (i. e., baseline context) or culturally-biased pictures (i.e., congruent context where culture matched the language to be spoken or incongruent context where culture mismatched the language to be spoken). Results showed an asymmetric switch cost with larger costs for L2 in the congruent context as compared with the baseline and incongruent contexts, but the reversed language dominance effect was not changed across contexts, suggesting that cultural context plays a critical role in modulating reactive but not proactive language control. These findings reveal the dynamic nature of language control in bilinguals and have important implications for the current models of bilingual language control.

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

The heated debate regarding bilingual cognitive advantages remains ongoing. While there are many studies supporting positive cognitive effects of bilingualism, recent meta-analyses have concluded that there is no consistent evidence for a bilingual advantage. In this article we focus on several theoretical concerns. First, we discuss changes in theoretical frameworks, which have led to the development of insufficiently clear theories and hypotheses that are difficult to falsify. Next, we discuss the development of looking at bilingual experiences and the need to better understand language control. Last, we argue that the move from behavioural studies to a focus on brain plasticity is not going to solve the debate on cognitive effects, especially not when brain changes are interpreted in the absence of behavioural differences. Clearer theories on both behavioural and neural effects of bilingualism are needed. However, to achieve this, a solid understanding of both bilingualism and executive functions is needed first.

Assessing the Evidence for Asymmetrical Switch Costs and Reversed Language Dominance Effects - A Meta-Analysis

Two seemingly counterintuitive phenomena - asymmetrical language switch costs and the reversed language dominance effect - prove to be particularly controversial in the literature on language control. Asymmetrical language switch costs refer to the larger costs for switching into the dominant language compared to switching into the less dominant language, both relative to staying in either one language. The reversed language dominance effect refers to longer reaction times when in the more dominant of the two languages in situations that require frequent language switching (i.e., mixed-language blocks). The asymmetrical language switch costs are commonly taken as an index for processes of transient, reactive inhibitory language control, whereas the reversed language dominance effect is taken as an index for sustained, proactive inhibitory language control. In the present meta-analysis, we set out to establish the empirical evidence for these two phenomena using a Bayesian linear mixed effects modelling approach. Despite the observation of both phenomena in some studies, our results suggest that overall, there is little evidence for the generality and robustness of these two effects, and this holds true even when conditions - such as language proficiency and preparation time manipulations - were included as moderators of these phenomena. We conclude that asymmetrical switch costs and the reversed language dominance effect are important for theory development, but their utility for theory testing is limited due to their lack of robustness and the absence of confirmed moderatory variables.

Language Dominance and Sociolinguistic Experience Are Related to Language Control and Domain-General Monitoring Control: An Investigation in Bilinguals Who Live in a Minority/Majority Sociolinguistic Setting

Bilingual language control in production tasks with language switches is supposed to be linked to domain-general cognitive control. In the present study, we investigated the role of language dominance, measured on a continuous scale, in the relationship between measures of language control elicited through language switching in a picture naming task and non-linguistic cognitive control induced by stimulus-response interference in a Simon task. In our sample of bilinguals who speak both a minority and majority language (language pair of Uyghur-Chinese), the results showed that as bilinguals were more L2-dominant, a pattern of reversed asymmetry switch costs in language control, i.e., larger L2 than L1 switch costs, was observed. Furthermore, the findings showed that recent exposure to the L1 minority language was associated with the change in language switch costs in terms of both response latencies and accuracy rates. This suggests a role for sociolinguistic context in bilingual language control. Concerning cross-domain generality, globally sustained language control was found to be correlated with domain-general monitoring control in response latencies for all bilingual participants. It lends support to the idea that bilinguals tap into monitoring control in the context of language switching. Additionally, the cross-domain overlap was found between two non-equivalent measures (global language control vs. cognitive inhibitory control) in response latencies, specifically for L1-dominant bilinguals. This suggests that language dominance may have an impact on cross-domain generality in language-switching processes.

Translation Distractors Facilitate Production in Single- and Mixed-Language Picture Naming

In the picture-word interference (PWI) task, semantically related distractors slow production, while translation-equivalent distractors speed it, possibly implying a language-specific bilingual production system (Costa, Miozzo & Caramazza, 1999). However, in most previous PWI studies bilinguals responded in just one language, an artificial task restriction. We investigated translation facilitation effects in PWI with language switching. Spanish-English bilinguals named pictures in single- or mixed-language-response blocks, with distractors in the target language (Experiment 1), or in the non-target language (Experiment 2). Both experiments replicated previously reported translation facilitation effects in both single-language and mixed-language-response blocks. However, language dominance was reversed in mixed-language response blocks, implying inhibition of the dominant language and competition between languages. These results may be explained by a language non-specific selection model in which bilinguals do not restrict selection to one language, with translation facilitation being caused by facilitation at the semantic level offsetting competition at the lexical level.

Codeswitching: A Bilingual Toolkit for Opportunistic Speech Planning

The ability to engage in fluent codeswitching is a hallmark of the flexibility and creativity of bilingual language use. Recent discoveries have changed the way we think about codeswitching and its implications for language processing and language control. One is that codeswitching is not haphazard, but subject to unique linguistic and cognitive constraints. Another is that not all bilinguals codeswitch, but those who do, exhibit usage patterns conforming to community-based norms. However, less is known about the cognitive processes that regulate and promote the likelihood of codeswitched speech. We review recent empirical studies and provide corpus evidence that highlight how codeswitching serves as an opportunistic strategy for optimizing performance in cooperative communication. From this perspective, codeswitching is part and parcel of a toolkit available to bilingual codeswitching speakers to assist in language production by allowing both languages to remain active and accessible, and therefore providing an alternative means to convey meaning, with implications for bilingual speech planning and language control more generally.

Whole-Language and Item-Specific Inhibition in Bilingual Language Switching: The Role of Domain-General Inhibitory Control

A prominent theory of bilingual speech production holds that appropriate language selection is achieved via inhibitory control. Such inhibition may operate on the whole-language and/or item-specific level. In this study, we examined these two levels of control in parallel, by introducing a novel element into the traditional cued language switching paradigm: half of the stimuli were univalent (each required naming in the same language every time it appeared), and the other half were bivalent (each required naming in different languages on different trials). Contrasting switch and stay trials provided an index for whole-language inhibition, while contrasting bivalent and univalent stimuli provided an index for item-specific inhibition. We then investigated the involvement of domain-general brain mechanisms in these two levels of language control. Neuroimaging studies report activation of the pre-supplementary motor area (pre-SMA), a key region in the executive control brain network, during language switching tasks. However, it is unclear whether or not the pre-SMA plays a causal role in language control, and at which level it exerts control. Using repetitive transcranial magnetic stimulation (TMS) to transiently disrupt the pre-SMA, we observed an essential role of this brain region in general speech execution, while evidence for its specific involvement in each level of inhibition remains inconclusive.

Processing Code-Switches in the Presence of Others: An ERP Study

Code-switching is highly socially constrained. For instance, code-switching is only felicitous when those present are fluent in both languages. This means that bilinguals need to dynamically adjust their language control and expectation of code-switching to the current social situation or context. The aim of the present EEG study was to investigate how and when language control in the comprehension of code-switches is affected by the assumed language knowledge of others in the context. Spanish-English bilinguals read sentences with and without code-switches together with another Spanish-English bilingual or with an English monolingual. Switches elicited an early fronto-central positivity. This effect was smaller overall when a bilingual was present at the start of the study. In addition, the late positive complex found for switches was smaller when a bilingual was present rather than a monolingual, but only for those participants who were sensitive to the other's language knowledge in their off-line judgments. These findings suggest that the bilinguals in our study expected and activated both languages when initially paired with a bilingual and that they more easily accommodated code-switches, in the presence of a bilingual than in the presence of a monolingual. Our findings support the view that language control can be modulated by the perceived language knowledge of others present, and are compatible with a dynamic control model of bilingual language comprehension.

Cognitive and Linguistic Predictors of Language Control in Bilingual Children

In order to communicate effectively with a variety of conversation partners and in a variety of settings, bilingual children must develop language control, the ability to control which language is used for production. Past work has focused on linguistic skills as the limiting factor in children's ability to control their language choice, while cognitive control has been the focus of adult models of language control. The current study examined the effects of both language ability and cognitive control on language control in 4-6 year old Spanish/English bilingual children with a broad range of language skills, including those with low skills in both languages. To measure language control, children participated in an interactive scripted confederate dialogue paradigm in which they took turns describing picture scenes with video partners who presented themselves as monolingual speakers of English or monolingual speakers of Spanish. The paradigm had two conditions: a single-language context, in which children interacted with only one partner, and a dual-language context, in which children needed to switch between languages to address different partners. The Dimensional Change Card Sort (DCCS) indexed cognitive control. The findings revealed an overall effect of language ability, such that children with lower language skills were more likely to produce words in the language not understood by their conversation partner. There was also an effect of cognitive control on children's ability to adjust to the dual-language context. Based on these findings, we suggest that a model of language control in children should consider both linguistic and cognitive factors. However, language ability appears to be the main limiting factor, with cognitive control playing a more restricted role in adapting to a dual-language context.

Turning languages on and off: Switching into and out of code-blends reveals the nature of bilingual language control

When spoken language (unimodal) bilinguals switch between languages, they must simultaneously inhibit 1 language and activate the other language. Because American Sign Language (ASL)-English (bimodal) bilinguals can switch into and out of code-blends (simultaneous production of a sign and a word), we can tease apart the cost of inhibition (turning a language off) and activation (turning a language on). Results from a cued picture-naming task with 43 bimodal bilinguals revealed a significant cost to turn off a language (switching out of a code-blend), but no cost to turn on a language (switching into a code-blend). Switching from single to dual lexical retrieval (adding a language) was also not costly. These patterns held for both languages regardless of default language, that is, whether switching between speaking and code-blending (English default) or between signing and code-blending (ASL default). Overall, the results support models of bilingual language control that assume a primary role for inhibitory control and indicate that disengaging from producing a language is more difficult than engaging a new language. (PsycINFO Database Record (c) 2020 APA, all rights reserved).

Functional connectivity reveals dissociable ventrolateral prefrontal mechanisms for the control of multilingual word retrieval

This functional magnetic resonance imaging study established that different portions of the ventrolateral prefrontal cortex (vlPFC) support reactive and proactive language control processes during multilingual word retrieval. The study also examined whether proactive language control consists in the suppression of the nontarget lexicon. Healthy multilingual volunteers participated in a task that required them to name pictures alternately in their dominant and less‐dominant languages. Two crucial variables were manipulated: the cue‐target interval (CTI) to either engage (long CTI) or prevent (short CTI) proactive control processes, and the cognate status of the to‐be‐named pictures (noncognates vs. cognates) to capture selective pre‐activation of the target language. The results of the functional connectivity analysis showed a clear segregation between functional networks related to mid‐vlPFC and anterior vlPFC during multilingual language production. Furthermore, the results revealed that multilinguals engage in proactive control to prepare the target language. This proactive modulation, enacted by anterior vlPFC, is achieved by boosting the activation of lexical representations in the target language. Finally, control processes supported by both mid‐vlPFC and the left inferior parietal lobe, were similarly engaged by reactive and proactive control, possibly exerted on phonological representations to reduce cross‐language interference.

Semantic Processing in Bilingual Aphasia: Evidence of Language Dependency

Individuals with aphasia frequently show lexical retrieval deficits due to increased interference of semantically related competitors, a phenomenon that can be observed in tasks such as naming pictures grouped by semantic category. These deficits are explained in terms of impaired semantic control, a set of abilities that are to some extent dependent upon executive control (EC). However, the extent to which semantic control abilities can be affected in a second and non-dominant language has not been extensively explored. Additionally, findings in healthy individuals are inconclusive regarding the degree to which semantic processing is shared between languages. In this study, we explored the effect of brain damage on semantic processing by comparing the performance of bilingual individuals with aphasia on tasks involving semantic control during word production and comprehension. Furthermore, we explored whether semantic deficits are related to domain-general EC deficits. First, we investigated the naming performance of Catalan-Spanish bilinguals with fluent aphasia and age-matched healthy controls on a semantically blocked cyclic naming task in each of their two languages (Catalan and Spanish). This task measured semantic interference in terms of the difference in naming latencies between pictures grouped by the same semantic category or different categories. Second, we explored whether lexical deficits extend to comprehension by testing participants in a word-picture matching task during a mixed language condition. Third, we used a conflict monitoring task to explore the presence of EC deficits in patients with aphasia. We found two main results. First, in both language tasks, bilingual patients' performances were more affected than those of healthy controls when they performed the task in their non-dominant language. Second, there was a significant correlation between the speed of processing on the EC task and the magnitude of the semantic interference effect exclusively in the non-dominant language. Taken together, these results suggest that lexical retrieval may be selectively impaired in bilinguals within those conditions where semantic competition is higher, i.e.,- in their non-dominant language; this could possibly be explained by an excessive amount of inhibition placed upon this language. Moreover, lexico-semantic impairments seem to be at least somewhat related to conflict monitoring deficits, suggesting a certain degree of overlap between EC and semantic control.

How bilingual experience and executive control influence development in language control among bilingual children

This longitudinal study investigates whether the development in executive control and bilingual experience predicts change in language control in bilingual children. Children were tested twice over the course of 1 year, using the language-switching paradigm and the Simon task. The participants were Japanese-English bilingual "returnee" children (ages 7-13), who returned to their first language (L1) environment after spending some years in a second language (L2) dominant environment. Testing these children upon their return to the L1 environment allowed us to disentangle the effect of age from bilingual experience, as they experienced an increase in age but a decrease in L2 exposure over time. Children who had less L2 exposure showed smaller improvement in baseline performance when naming pictures in English (i.e., when English was relevant across all trials). Moreover, development in trials where children had to switch between languages were modulated by development in executive control. That is, children who increased their performance in the English mixed repetition trials also performed better on the executive control task over time. Thus, development in executive control modulated change in language control among bilingual children, suggesting a positive relationship between language control and executive control in children's development.

Does Extreme Language Control Training Improve Cognitive Control? A Comparison of Professional Interpreters, L2 Teachers and Monolinguals

There is currently a lively debate in the literature whether bilingualism leads to enhanced cognitive control or not. Recent evidence suggests that knowledge of more than one language does not always suffice for the manifestation of a bilingual cognitive control advantage. As a result, ongoing research has focused on modalities of bilingual language use that may interact with the bilingual advantage. In this study, we explored the cognitive control performance of simultaneous interpreters. These highly proficient bilinguals comprehend information in one language while producing in the other language, which is a complex skill requiring high levels of language control. In a first experiment, we compared professional interpreters to monolinguals. Data were collected on interference suppression (flanker task), prepotent response inhibition (Simon task), and short-term memory (digit span task). The results showed that the professional interpreters performed similarly to the monolinguals on all measures. In Experiment 2, we compared professional interpreters to monolinguals and second language teachers. Data were collected on interference suppression (advanced flanker task), prepotent response inhibition (advanced flanker task), attention (advanced flanker task), short-term memory (Hebb repetition paradigm), and updating (n-back task). We found converging evidence for our finding that experience in interpreting may not lead to superior interference suppression, prepotent response inhibition, and short-term memory. In fact, our results showed that the professional interpreters performed similarly to both the monolinguals and the second language teachers on all tested cognitive control measures. We did, however, find anecdotal evidence for a (small) advantage in short-term memory for interpreters relative to monolinguals when analyzing composite scores of both experiments together. Taken together, the results of the current study suggest that interpreter experience does not necessarily lead to general cognitive control advantages. However, there may be small interpreter advantages in short-term memory, suggesting that this might be an important cognitive control aspect of simultaneous interpreting. The results are discussed in the light of ongoing debates about bilingual cognitive control advantages.

Neural basis of bilingual language control

Acquiring and speaking a second language increases demand on the processes of language control for bilingual as compared to monolingual speakers. Language control for bilingual speakers involves the ability to keep the two languages separated to avoid interference and to select one language or the other in a given conversational context. This ability is what we refer with the term "bilingual language control" (BLC). It is now well established that the architecture of this complex system of language control encompasses brain networks involving cortical and subcortical structures, each responsible for different cognitive processes such as goal maintenance, conflict monitoring, interference suppression, and selective response inhibition. Furthermore, advances have been made in determining the overlap between the BLC and the nonlinguistic executive control networks, under the hypothesis that the BLC processes are just an instantiation of a more domain-general control system. Here, we review the current knowledge about the neural basis of these control systems. Results from brain imaging studies of healthy adults and on the performance of bilingual individuals with brain damage are discussed.

Recognizing the Effects of Language Mode on the Cognitive Advantages of Bilingualism

For bilinguals, it is argued that a cognitive advantage can be linked to the constant management and need for conflict resolution that occurs when the two languages are co-activated (Bialystok, 2015). Language mode (Grosjean, 1998, 2001) is a significant variable that defines and shapes the language experiences of bilinguals and consequently, the cognitive advantages of bilingualism. Previous work, however, has not sufficiently tested the effects of language mode on the bilingual experience. In this brief conceptual analysis, we discuss the significance of language mode in bilingual work on speech perception, production, and reading. We offer possible explanations for conflicting findings and ways in which future work should control for its modulating effects.

Contributions of nonlinguistic task-shifting to language control in bilingual children

Language control, bilinguals' ability to regulate which language is used, has been posited to recruit domain-general cognitive control. However, studies relating language control and cognitive control have yielded mixed results in adults and have not been undertaken in children. The current study examined the contributions of nonlinguistic task-shifting to language control in Spanish-English bilingual children (ages 5-7) during a cued-switch picture-naming task. Language control was assessed at two levels: (1) cross-language errors, which indexed the success of language selection, and (2) naming speed, which indexed the efficiency of lexical selection. Nonlinguistic task-shifting was a robust predictor of children's cross-language errors, reflecting a role for domain-general cognitive control during language selection. However, task-shifting predicted naming speed only in children's non-dominant language, suggesting a more nuanced role for cognitive control in the efficiency of selecting a particular lexical target.

Bilingual infants control their languages as they listen

Infants growing up in bilingual homes learn two languages simultaneously without apparent confusion or delay. However, the mechanisms that support this remarkable achievement remain unclear. Here, we demonstrate that infants use language-control mechanisms to preferentially activate the currently heard language during listening. In a naturalistic eye-tracking procedure, bilingual infants were more accurate at recognizing objects labeled in same-language sentences ("Find the dog!") than in switched-language sentences ("Find the chien!"). Measurements of infants' pupil size over time indicated that this resulted from increased cognitive load during language switches. However, language switches did not always engender processing difficulties: the switch cost was reduced or eliminated when the switch was from the nondominant to the dominant language, and when it crossed a sentence boundary. Adults showed the same patterns of performance as infants, even though target words were simple and highly familiar. Our results provide striking evidence from infancy to adulthood that bilinguals monitor their languages for efficient comprehension. Everyday practice controlling two languages during listening is likely to explain previously observed bilingual cognitive advantages across the lifespan.

Bilingual Language Switching in the Laboratory versus in the Wild: The Spatiotemporal Dynamics of Adaptive Language Control

For a bilingual human, every utterance requires a choice about which language to use. This choice is commonly regarded as part of general executive control, engaging prefrontal and anterior cingulate cortices similarly to many types of effortful task switching. However, although language control within artificial switching paradigms has been heavily studied, the neurobiology of natural switching within socially cued situations has not been characterized. Additionally, although theoretical models address how language control mechanisms adapt to the distinct demands of different interactional contexts, these predictions have not been empirically tested. We used MEG (RRID: NIFINV:nlx_inv_090918) to investigate language switching in multiple contexts ranging from completely artificial to the comprehension of a fully natural bilingual conversation recorded “in the wild.” Our results showed less anterior cingulate and prefrontal cortex involvement for more natural switching. In production, voluntary switching did not engage the prefrontal cortex or elicit behavioral switch costs. In comprehension, while laboratory switches recruited executive control areas, fully natural switching within a conversation only engaged auditory cortices. Multivariate pattern analyses revealed that, in production, interlocutor identity was represented in a sustained fashion throughout the different stages of language planning until speech onset. In comprehension, however, a biphasic pattern was observed: interlocutor identity was first represented at the presentation of the interlocutor and then again at the presentation of the auditory word. In all, our findings underscore the importance of ecologically valid experimental paradigms and offer the first neurophysiological characterization of language control in a range of situations simulating real life to various degrees.

SIGNIFICANCE STATEMENT Bilingualism is an inherently social phenomenon, interactional context fully determining language choice. This research addresses the neural mechanisms underlying multilingual individuals' ability to successfully adapt to varying conversational contexts both while speaking and listening. Our results showed that interactional context critically determines language control networks' engagement: switching under external constraints heavily recruited prefrontal control regions, whereas natural, voluntary switching did not. These findings challenge conclusions derived from artificial switching paradigms, which suggested that language switching is intrinsically effortful. Further, our results predict that the so-called bilingual advantage should be limited to individuals who need to control their languages according to external cues and thus would not occur by virtue of an experience in which switching is fully free.

Functional Connectivity Reveals Which Language the "Control Regions" Control during Bilingual Production

Bilingual studies have revealed critical roles for the dorsal anterior cingulate cortex (dACC) and the left caudate nucleus (Lcaudate) in controlling language processing, but how these regions manage activation of a bilingual’s two languages remains an open question. We addressed this question by identifying the functional connectivity (FC) of these control regions during a picture-naming task by bimodal bilinguals who were fluent in both a spoken and a signed language. To quantify language control processes, we measured the FC of the dACC and Lcaudate with a region specific to each language modality: left superior temporal gyrus (LSTG) for speech and left pre/postcentral gyrus (LPCG) for sign. Picture-naming occurred in either a single- or dual-language context. The results showed that in a single-language context, the dACC exhibited increased FC with the target language region, but not with the non-target language region. During the dual-language context when both languages were alternately the target language, the dACC showed strong FC to the LPCG, the region specific to the less proficient (signed) language. By contrast, the Lcaudate revealed a strong connectivity to the LPCG in the single-language context and to the LSTG (the region specific to spoken language) in the dual-language context. Our findings suggest that the dACC monitors and supports the processing of the target language, and that the Lcaudate controls the selection of the less accessible language. The results support the hypothesis that language control processes adapt to task demands that vary due to different interactional contexts.

Psycholinguistic, cognitive, and neural implications of bimodal bilingualism

Bimodal bilinguals, fluent in a signed and a spoken language, exhibit a unique form of bilingualism because their two languages access distinct sensory-motor systems for comprehension and production. Differences between unimodal and bimodal bilinguals have implications for how the brain is organized to control, process, and represent two languages. Evidence from code-blending (simultaneous production of a word and a sign) indicates that the production system can access two lexical representations without cost, and the comprehension system must be able to simultaneously integrate lexical information from two languages. Further, evidence of cross-language activation in bimodal bilinguals indicates the necessity of links between languages at the lexical or semantic level. Finally, the bimodal bilingual brain differs from the unimodal bilingual brain with respect to the degree and extent of neural overlap for the two languages, with less overlap for bimodal bilinguals.

Does Bilingual Language Control Decline in Older Age?

We investigated age-related decline of bilingual language control. Thirteen older and 13 younger bilinguals performed a verbal fluency task (completing the same letter and semantic categories in each language and switching languages after every category), and a non-linguistic flanker task. In letter fluency, bilinguals produced fewer correct responses after switching languages, suggesting inhibition of the previously-used language. However, this testing-order effect did not differ between groups and older bilinguals produced few wrong-language intrusions, implying intact ability to apply inhibition in older age. In contrast, age-related deficits in the flanker task were robust, implying dissociations between language control and domain-general executive control. In semantic fluency, there were no testing-order effects but older bilinguals produced more intrusions than younger bilinguals, and more intrusions than in letter fluency. Thus, bilinguals may flexibly modulate the degree of inhibition when they can benefit from semantic priming between languages, but less efficiently so in older age.

Bilingual Language Control in Perception versus Action: MEG Reveals Comprehension Control Mechanisms in Anterior Cingulate Cortex and Domain-General Control of Production in Dorsolateral Prefrontal Cortex

For multilingual individuals, adaptive goal-directed behavior as enabled by cognitive control includes the management of two or more languages. This work used magnetoencephalography (MEG) to investigate the degree of neural overlap between language control and domain-general cognitive control both in action and perception. Highly proficient Arabic-English bilingual individuals participated in maximally parallel language-switching tasks in production and comprehension as well as in analogous tasks in which, instead of the used language, the semantic category of the comprehended/produced word changed. Our results indicated a clear dissociation of language control mechanisms in production versus comprehension. Language-switching in production recruited dorsolateral prefrontal regions bilaterally and, importantly, these regions were similarly recruited by category-switching. Conversely, effects of language-switching in comprehension were observed in the anterior cingulate cortex and were not shared by category-switching. These results suggest that bilingual individuals rely on adaptive language control strategies and that the neural involvement during language-switching could be extensively influenced by whether the switch is active (e.g., in production) or passive (e.g., in comprehension). In addition, these results support that humans require high-level cognitive control to switch languages in production, but the comprehension of language switches recruits a distinct neural circuitry. The use of MEG enabled us to obtain the first characterization of the spatiotemporal profile of these effects, establishing that switching processes begin ∼ 400 ms after stimulus presentation.

SIGNIFICANCE STATEMENT

This research addresses the neural mechanisms underlying multilingual individuals' ability to successfully manage two or more languages, critically targeting whether language control is uniform across linguistic domains (production and comprehension) and whether it is a subdomain of general cognitive control. The results showed that language production and comprehension rely on different networks: whereas language control in production recruited domain-general networks, the brain bases of switching during comprehension seemed language specific. Therefore, the crucial assumption of the bilingual advantage hypothesis, that there is a close relationship between language control and general cognitive control, seems to only hold during production.

Voluntary language switching in English-Spanish bilingual children

Although bilingual children frequently switch between languages, the psycholinguistic mechanisms underlying the emerging ability to control language choice are unknown. We examined the mechanisms of voluntary language switching in English-Spanish bilingual children during a picture-naming task under two conditions: 1) single-language naming in English and in Spanish; 2) either-language naming, when the children could use whichever language they wanted. The mechanism of inhibitory control was examined by analyzing local switching costs and global mixing costs. The mechanism of lexical accessibility was examined by analyzing the properties of the items children chose to name in their non-dominant language. The children exhibited significant switching costs across both languages and asymmetrical mixing costs; they also switched into their non-dominant language most frequently on highly accessible items. These findings suggest that both lexical accessibility and inhibition contribute to language choice during voluntary language switching in children.

Multiple levels of bilingual language control: evidence from language intrusions in reading aloud

Bilinguals rarely produce words in an unintended language. However, we induced such intrusion errors (e.g., saying el instead of he) in 32 Spanish-English bilinguals who read aloud single-language (English or Spanish) and mixed-language (haphazard mix of English and Spanish) paragraphs with English or Spanish word order. These bilinguals produced language intrusions almost exclusively in mixed-language paragraphs, and most often when attempting to produce dominant-language targets (accent-only errors also exhibited reversed language-dominance effects). Most intrusion errors occurred for function words, especially when they were not from the language that determined the word order in the paragraph. Eye movements showed that fixating a word in the nontarget language increased intrusion errors only for function words. Together, these results imply multiple mechanisms of language control, including (a) inhibition of the dominant language at both lexical and sublexical processing levels, (b) special retrieval mechanisms for function words in mixed-language utterances, and (c) attentional monitoring of the target word for its match with the intended language.

The impact of early bilingualism on controlling a language learned late: an ERP study

This study asks whether early bilingual speakers who have already developed a language control mechanism to handle two languages control a dominant and a late acquired language in the same way as late bilingual speakers. We therefore, compared event-related potentials in a language switching task in two groups of participants switching between a dominant (L1) and a weak late acquired language (L3). Early bilingual late learners of an L3 showed a different ERP pattern (larger N2 mean amplitude) as late bilingual late learners of an L3. Even though the relative strength of languages was similar in both groups (a dominant and a weak late acquired language), they controlled their language output in a different manner. Moreover, the N2 was similar in two groups of early bilinguals tested in languages of different strength. We conclude that early bilingual learners of an L3 do not control languages in the same way as late bilingual L3 learners –who have not achieved native-like proficiency in their L2– do. This difference might explain some of the advantages early bilinguals have when learning new languages.

Qualitative Differences between Bilingual Language Control and Executive Control: Evidence from Task-Switching

Previous research has shown that highly proficient bilinguals have comparable switch costs in both directions when they switch between languages (L1 and L2), the so-called "symmetrical switch cost" effect. Interestingly, the same symmetry is also present when they switch between L1 and a much weaker L3. These findings suggest that highly proficient bilinguals develop a language control system that seems to be insensitive to language proficiency. In the present study, we explore whether the pattern of symmetrical switch costs in language switching tasks generalizes to a non-linguistic switching task in the same group of highly proficient bilinguals. The end goal of this is to assess whether bilingual language control (bLC) can be considered as subsidiary to domain-general executive control (EC). We tested highly proficient Catalan-Spanish bilinguals both in a linguistic switching task and in a non-linguistic switching task. In the linguistic task, participants named pictures in L1 and L2 (Experiment 1) or L3 (Experiment 2) depending on a cue presented with the picture (a flag). In the non-linguistic task, the same participants had to switch between two card sorting rule-sets (color and shape). Overall, participants showed symmetrical switch costs in the linguistic switching task, but not in the non-linguistic switching task. In a further analysis, we observed that in the linguistic switching task the asymmetry of the switch costs changed across blocks, while in the non-linguistic switching task an asymmetrical switch cost was observed throughout the task. The observation of different patterns of switch costs in the linguistic and the non-linguistic switching tasks suggest that the bLC system is not completely subsidiary to the domain-general EC system.

Parallel recovery in a trilingual speaker: the use of the Bilingual Aphasia Test as a diagnostic complement to the Comprehensive Aphasia Test

We illustrate the value of the Bilingual Aphasia Test in the diagnostic assessment of a trilingual speaker post-stroke living in England for whom English was a non-native language. The Comprehensive Aphasia Test is routinely used to assess patients in English, but only in combination with the Bilingual Aphasia Test is it possible and practical to provide a full picture of the language impairment. We describe our test selection and the assessment it allows us to make.

Language control in different contexts: the behavioral ecology of bilingual speakers

This paper proposes that different experimental contexts (single or dual language contexts) permit different neural loci at which words in the target language can be selected. However, in order to develop a fuller understanding of the neural circuit mediating language control we need to consider the community context in which bilingual speakers typically use their two languages (the behavioral ecology of bilingual speakers). The contrast between speakers from code-switching and non-code-switching communities offers a way to increase our understanding of the cortical, subcortical and, in particular, cerebellar structures involved in language control. It will also help us identify the non-verbal behavioral correlates associated with these control processes

Language control and parallel recovery of language in individuals with aphasia

Background: The causal basis of the different patterns of language recovery following stroke in bilingual speakers is not well understood. Our approach distinguishes the representation of language from the mechanisms involved in its control. Previous studies have suggested that difficulties in language control can explain selective aphasia in one language as well as pathological switching between languages. Here we test the hypothesis that difficulties in managing and resolving competition will also be observed in those who are equally impaired in both their languages even in the absence of pathological switching.Aims: To examine difficulties in language control in bilingual individuals with parallel recovery in aphasia and to compare their performance on different types of conflict task.Methods & Procedures: Two right-handed, non-native English-speaking participants who showed parallel recovery of two languages after stroke and a group of non-native English-speaking, bilingual controls described a scene in English and in their first language and completed three explicit conflict tasks. Two of these were verbal conflict tasks: a lexical decision task in English, in which individuals distinguished English words from non-words, and a Stroop task, in English and in their first language. The third conflict task was a non-verbal flanker task.Outcomes & Results: Both participants with aphasia were impaired in the picture description task in English and in their first language but showed different patterns of impairment on the conflict tasks. For the participant with left subcortical damage, conflict was abnormally high during the verbal tasks (lexical decision and Stroop) but not during the non-verbal flanker task. In contrast, for the participant with extensive left parietal damage, conflict was less abnormal during the Stroop task than the flanker or lexical decision task.Conclusions: Our data reveal two distinct control impairments associated with parallel recovery. We stress the need to explore the precise nature of control problems and how control is implemented in order to develop fuller causal accounts of language recovery patterns in bilingual aphasia.