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

Combining Languages in Bilingual Input: Using Experimental Evidence to Formulate Bilingual Exposure Strategies

PURPOSE

Traditional approaches to studying bilingual language development through bilingual-monolingual comparisons are deeply flawed. They are also insufficient as the evidence base for informing advice to bilingual parents regarding the optimal bilingual exposure strategy and for supporting the formulation of bilingual intervention approaches. The purpose of this review article is to provide an overview of empirical studies that have queried the question of how different types of dual-language input shape learning and language outcomes in bilingual children.

METHOD

We rely on tightly controlled experimental studies of word learning in Spanish-English bilingual children, where we contrast children's learning in dual-language conditions (defined as distributed exposure and code-switched input) to a single-language condition in a within-subjects design.

RESULTS

Word-learning studies querying the role of distributed exposure indicated that distribution of exposures across Spanish and English reduced children's performance in comparison to English-only exposure. However, this effect was rooted in the abrupt switch from Spanish to English rather than distributed exposure itself. In contrast, an experiment designed to test the role of code-switched context on children's word learning revealed that code-switched context where switches resembled naturalistic code-switching behaviors enhanced learning in Spanish-English bilingual children. Notably, across different studies, children with weaker language skills (developmental language disorder) were no more affected by dual-language input than children with typical language skills.

CONCLUSIONS

Together, experimental studies of word learning indicate that bilingual children can effectively learn from dual-language input but that different ways of combining languages in the input to bilingual children can have distinct consequences for learning. Ultimately, word-learning experiments, beyond answering critical questions regarding bilingual learning, can serve as an effective bridge between laboratory-based work and intervention studies whose goal it is to discover the optimal way of combining languages in the input to bilingual children with communication impairments.

PRESENTATION VIDEO

https://doi.org/10.23641/asha.23929515.

Language Control and Code-Switching in Bilingual Children With Developmental Language Disorder

PURPOSE

The current study examined language control and code-switching in bilingual children with developmental language disorder (DLD) compared to bilingual peers with typical language development (TLD). In addition, proficiency in each language and cognitive control skills were examined as predictors of children's tendency to engage in cross-speaker and intrasentential code-switching.

METHOD

The participants were 62 Spanish/English bilingual children, ages 4;0-6;11 (years;months), including 15 children with DLD and 47 children with TLD. In a scripted confederate dialogue task to measure language control, children took turns describing picture scenes with video partners who were monolingual speakers of English or Spanish. The Dimensional Change Card Sort indexed cognitive control, the Bilingual English Spanish Assessment assisted in identifying DLD, and parent ratings from the Inventory to Assess Language Knowledge indexed proficiency in Spanish and English.

RESULTS

Children with DLD were more likely to engage in cross-speaker code-switching from Spanish to English (i.e., responding in English when addressed in Spanish) than children with TLD, even when controlling for proficiency in each language. Intrasentential code-switching (i.e., integrating both languages within an utterance) did not differ between groups. Cognitive control was more associated with cross-speaker than with intrasentential code-switching.

CONCLUSIONS

These findings highlight the need to consider cross-speaker and intrasentential code-switching separately when seeking distinguishing features of code-switching in bilingual children with DLD. The use of increased cross-speaker code-switching by children with DLD especially with Spanish speakers highlights the need for increased support of home language use.

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

BACKGROUND

The neural networks underpinning language control and domain-general executive functions overlap in bilinguals, but existing evidence is mainly correlative. Here, we present the first neurofunctional evidence for a transfer effect between (domain-general) inhibitory control and language control through training. We trained Chinese-English bilinguals for 8 days using a Simon task taxing the inhibitory control system, whilst an active control group was trained with a color judgment task that does not tax the inhibitory control system. All participants performed a language-switching task before and after training. It has been suggested that the activity of the left DLPFC was associated with domain-general top-down cognitive control (Macdonald et al. Science 288: 1835-1838, 2000) and bilingual language control (Wang et al. Neuroimage 35: 862-870, 2007). In addition, the dACC was closely related to the conflict detection (Abutalebi et al. Cereb Cortex 18:1496-1505, 2008). Last, the activity of the left caudate has been linked with lexical selection (Abutalebi et al. Cereb Cortex 18:1496-1505, 2008), especially the selection of the weak language (Abutalebi et al. Cortex 49: 905-911, 2013). Therefore, we focused on these three regions of interest (ROIs) where neural changes associated with transfer were expected to occur.

RESULTS

The results showed a negative correlation between changes in activation levels in the left dorsolateral prefrontal cortex (DLPFC) and changes in the switch cost magnitude in the language-switching task in the training group but not in the control group, suggesting that the DLPFC plays a critical role in the transfer effect from domain-general executive functions to language control. However, there was no measurable effect in the anterior cingulate cortex or left caudate nucleus, suggesting that the inhibitory control training increased the neural efficiency for language production in bilinguals in terms of attention shifting and conflict resolution, but the training did not affect conflict detection and lexical selection.

CONCLUSION

These findings showed how cognitive training evidence can help establish a causational link between the neural basis of domain-general executive functions and language control in bilinguals.

Grammatical processing in two languages: How individual differences in language experience and cognitive abilities shape comprehension in heritage bilinguals

Recent studies have demonstrated variation in language processing for monolingual and bilingual speakers alike, suggesting that only by considering individual differences will an accurate picture of the consequences of language experience be adequately understood. This approach can be illustrated in ERP research that has shown that sentence contexts that traditionally elicit a P600 component in response to a syntactic violation, elicit an N400 response for a subset of individuals. That result has been reported for monolingual speakers processing sentences in their L1 and also for bilinguals processing sentences in their L2. To date, no studies have compared variation in L1 and L2 ERP effects in the very same bilingual speakers. In the present paper, we do that by examining sentence processing in heritage bilinguals who acquired both languages from early childhood but for whom the L2 typically becomes the dominant language. Variation in ERPs produced by the non-dominant L1 and dominant L2 of heritage bilinguals was compared to variation found in monolingual L1 processing. The group-averaged results showed the smallest N400 and P600 responses in the native, but no longer dominant, L1 of heritage bilinguals, and largest in the monolinguals. Individual difference analyses linking ERP variation to working memory and language proficiency showed that working memory was the primary factor related to monolingual L1 processing, whereas bilinguals did not show this relationship. In contrast, proficiency was the primary factor related to ERP responses for no longer dominant L1 for bilinguals, but unrelated to monolingual L1 processing, whereas bilinguals' dominant L2 processing showed an intermediate relationship. Finally, the N400 was absent for bilinguals performing the task in the same language in which they initially learned to read, but significantly larger when bilinguals performed the task in the other language. The results support the idea that proficient bilinguals utilize the same underlying mechanisms to process both languages, although the factors that affect processing in each language may differ. More broadly, we find that bilingualism is an experience that opens the language system to perform fluidly under changing circumstances, such as increasing proficiency. In contrast, language processing in monolinguals was primarily related to relatively stable factors (working memory).

Processing of Code-Switched Sentences in Noise by Bilingual Children

Purpose The purpose of the current study was to examine the effects of code-switching on bilingual children's online processing and offline comprehension of sentences in the presence of noise. In addition, the study examined individual differences in language ability and cognitive control skills as moderators of children's ability to process code-switched sentences in noise. Method The participants were 50 Spanish-English bilingual children, ages 7;0-11;8 (years;months). Children completed an auditory moving window task to examine whether they processed sentences with code-switching more slowly and less accurately than single-language sentences in the presence of noise. They completed the Dimensional Change Card Sort task to index cognitive control and standardized language measures in English and Spanish to index relative language dominance and overall language ability. Results Children were significantly less accurate in answering offline comprehension questions about code-switched sentences presented in noise compared to single-language sentences, especially for their dominant language. They also tended to exhibit slower processing speed, but costs did not reach significance. Language ability had an overall effect on offline comprehension but did not moderate the effects of code-switching. Cognitive control moderated the extent to which offline comprehension costs were affected by language dominance. Conclusions The findings of the current study suggest that code-switching, especially in the presence of background noise, may place additional demands on children's ability to comprehend sentences. However, it may be the processing of the nondominant language, rather than code-switching per se, that is especially difficult in the presence of noise.

Language Differentiation Using Augmentative and Alternative Communication: An Investigation of Spanish-English Bilingual Children With and Without Language Impairments

Purpose Children with severe speech and language impairments growing up in dual language environments may communicate in more than one language using augmentative and alternative communication (AAC). This study investigated predictors of bilingual children's ability to differentiate between Spanish and English using an AAC iPad app during a cued language-switching task and examined whether switching between languages using AAC incurred a cognitive cost. Method Participants were 58 Spanish-English bilingual children ages 4;0-6;11 (years;months; 23 with language impairments). Children received standardized language and cognitive assessments and completed an experimental language-switching task in which they were asked to differentiate between languages using an AAC iPad app containing English and Spanish vocabulary layouts paired with voice output. Results Results of a binary logistic regression indicated that, when controlling for age, processing speed significantly predicted whether children were classified as high or low performers on the experimental task. Nonparametric tests indicated that switching between languages did not incur a cognitive cost as evidenced by similar response times on trials where participants were required to switch between languages compared to trials where they did not switch. Conclusion This study contributes to the understanding of how young bilingual children with and without language impairments conceptualize and discriminate between languages represented in a visual-graphic modality paired with speech output. Supplemental Material https://doi.org/10.23641/asha.13289330.

No Bilingual Benefits Despite Relations Between Language Switching and Task Switching

Previous research has shown that bilingual children outperform monolinguals on tasks testing cognitive control. Bilinguals' enhanced cognitive control is thought to be caused by the necessity to exert more language control in bilingual compared to monolingual settings. Surprisingly, between-group research of cognitive effects of bilingualism is hardly ever combined with within-group research that investigates relationships between language control and cognitive control. The present study compared 27 monolingual Dutch and 27 bilingual Turkish-Dutch children matched on age and fluid intelligence on their performance in a nonverbal switching task. Within the group of bilinguals, the relationship between nonverbal switching and language switching was examined. The results revealed no between-group differences on nonverbal switching. Within the bilingual sample, response times in the language switching and nonverbal switching tasks were related, although no relationships were found between accuracy, switching cost and mixing cost on both tasks. The results support the hypothesis that children utilize domain-general cognitive control in language switching, but this relationship does not entail that bilinguals have better cognitive control than monolinguals.

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.

Processing of code-switched sentences by bilingual children: Cognitive and linguistic predictors

Production studies of language switching have identified costs in the speed and/or accuracy of word production, but it is unclear whether processing costs are experienced by listeners as well. A related question is whether language control during comprehension recruits domain-general cognitive control. The current study examined processing of code-switching in Spanish-English bilingual children (ages 6;0-11;10) using an auditory moving window paradigm. Cognitive control was indexed by the Dimensional Change Card Sort. Children exhibited significant costs in processing speed when listening to code-switched sentences, but no costs in a measure of offline comprehension. The extent to which cognitive control skills moderated processing costs depended on the robustness of the language system: children with higher language skills exhibited a greater moderating effect of cognitive control. Taken together, the findings provide limited support for a role of cognitive control in children's code-switching processing and suggest that the processing costs incurred may be transitory.

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.