Bilingual advantages in executive control tasks are well documented, but it is not yet clear what degree or type of bilingualism leads to these advantages. To investigate this issue, we compared the performance of two bilingual groups and monolingual speakers in task-switching and language-switching paradigms. Spanish-English bilinguals, who reported switching between languages frequently in daily life, exhibited smaller task-switching costs than monolinguals after controlling for between-group differences in speed and parent education level. By contrast, Mandarin-English bilinguals, who reported switching languages less frequently than Spanish-English bilinguals, did not exhibit a task-switching advantage relative to monolinguals. Comparing the two bilingual groups in language-switching, Spanish-English bilinguals exhibited smaller costs than Mandarin-English bilinguals, even after matching for fluency in the non-dominant language. These results demonstrate an explicit link between language-switching and bilingual advantages in task-switching, while also illustrating some limitations on bilingual advantages.

This study investigated the possibility that lifelong bilingualism may lead to enhanced efficiency in the ability to shift between mental sets. We compared the performance of monolingual and fluent bilingual college students in a task-switching paradigm. Bilinguals incurred reduced switching costs in the task-switching paradigm when compared with monolinguals, suggesting that lifelong experience in switching between languages may contribute to increased efficiency in the ability to shift flexibly between mental sets. On the other hand, bilinguals did not differ from monolinguals in the differential cost of performing mixed-task as opposed to single-task blocks. Together, these results indicate that bilingual advantages in executive function most likely extend beyond inhibition of competing responses, and encompass flexible mental shifting as well.

We investigated the relationship between language control and executive control by testing three groups of bilinguals (104 participants) and 54 monolinguals in a training and transfer paradigm. Participants practiced either a language or a non-linguistic color/shape switching task and were tested one week later on both tasks. The color-shape task produced significant immediate improvement with training, which was maintained a week later, but exhibited no cross-task transfer effects. In the dominant-language, training effects did not persist after one week, and there were no transfer effects. In the non-dominant language there were significant training effects that lasted a week, and there was also transfer facilitation from prior practice with the color/shape task, which was limited to a reduction in mixing costs. Despite limited transfer, there were significant correlations between tasks in mixing costs for bilinguals, in switching costs for monolinguals, and in intrusion errors for all participants. Finally, the pattern of costs observed for the two tasks exhibited both similarities and differences across participants. These results imply a limited but significant role for executive control in bilingual language control, possibly playing a stronger role in facilitating non-dominant language production and in supporting the ability to monitor response outcomes to avoid errors.

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Bilingualism might prove to be an added burden for adults with ADHD, leading to reduced EF abilities. Alternatively, the current findings might be ascribed to over- or under-diagnosis of ADHD due to cultural differences between groups. These issues should be pursued in future research.

The current study examined automatic activation and semantic influences from the non-target language of different-script bilinguals during visual word processing. Thirty-four Arabic–Hebrew bilinguals and 34 native Hebrew controls performed a semantic relatedness task on visually presented Hebrew word pairs. In one type of critical trials, cognate primes between Arabic and Hebrew preceded related Hebrew target words. In a second type, false-cognate primes preceded Hebrew targets related to the Arabic meaning (but not the Hebrew meaning) of the false-cognate. Although Hebrew orthography is a fully reliable cue of language membership, facilitation on cognate trials and interference on false-cognate trials were observed for Arabic–Hebrew bilinguals. The activation of the non-target language was sufficient to influence participants’ semantic decisions in the target language, demonstrating simultaneous activation of both languages even for different-script bilinguals in a single language context. To discuss the findings we refine existing models of bilingual processing to accommodate different-script bilinguals.

Valian (2014) suggests that the messy state of the literature examining the effects of bilingualism on executive functioning (EF) stems from lack of clarity in how EFs are defined and measured, and from lack of control over other factors that can modulate EF. We argue that the lack of clarity in how bilingualism is defined and measured is no less problematic. We focus our commentary on two related issues.