The benefits of bilingualism on different domains of cognitive function have been reported extensively, supported by both behavioral measures and neuroimaging. However, less is known about the role age of second language acquisition plays and whether differences exist between sequential and simultaneous bilinguals in terms of attentional control.
In the article, “Early bilingualism, language attainment, and brain development,” Jonathan Berken reviews papers that help understand how the timing of language experience shapes brain structure and function. Specifically, Berken uses bilingualism to examine how early versus late experience of language affects brain organization. Bergen begins by reviewing papers that studied patterns of early maturation of language-related brain areas to understand optimal periods in language acquisition. Second, he focuses on the optimal period in bilingual language development, specifically the structural and functional brain differences in simultaneous bilinguals and sequential bilinguals. Next, this article looks at early bilingualism and the development of the language network, examining the effects of exposure to more than one language from birth. Finally, how the age of acquisition influences brain structure and function is explored; notably, Berken and colleagues found that bilinguals who acquired a second language beyond the optimal period utilize compensatory mechanisms to produce native-like speech; they also found a correlation between gray matter density in the left putamen and native-like articulation in highly proficient sequential bilinguals. In conclusion, the papers reviewed in this article all point to the benefits of acquiring two languages simultaneously in early childhood, as the mechanisms for neuroplasticity later in life are qualitatively and quantitatively different from those that begin and end in early childhood.
Less is known about how the benefits of acquiring two languages simultaneously at birth manifest in different cognitive domains later in early adulthood. Taking advantage of previous findings that found greater cognitive control in bilinguals, Brito et al. (2015) were interested in the interaction of different cognitive domains and specifically examined whether bilingual advantages in cognitive control could have an effect on memory encoding. They recruited college students who were simultaneous bilinguals, sequential bilinguals, or monolinguals and assessed their attention and memory. Attention was measured by a classification task where subjects were asked to identify words as concrete or abstract and objects as human-made or natural. During each trial, relevant or irrelevant stimuli were present to distract subjects; participants’ reaction times and the number of errors were measured. Subsequently, a memory task was employed where subjects were asked to identify the items they had seen previously during the classification task. Overall, they found that simultaneous bilinguals committed the fewest errors on the classification task with distractions, followed by sequential bilinguals and monolinguals who committed the most errors. On the other hand, the three groups did not differ much in their performance on the subsequent memory task. These two findings suggest that better performance on the classification task in simultaneous bilinguals was due to enhanced attentional control and not better memory recognition of relevant stimuli and less recognition of irrelevant stimuli.
Taken together, findings from these two papers support the benefits of early language acquisition at birth. Through neuroimaging, Berken et al. (2017) found that simultaneous bilinguals relied less on compensatory mechanisms and can more easily produce native-like speech when speaking in their second language. Even though Brito and colleagues (2015) failed to find a correlation between attention and memory at the group level between bilinguals and monolinguals, they still observed significantly better performance on the classification task in simultaneous bilinguals, suggesting additional advantages in attentional control over sequential bilinguals. Future studies could look at the interaction between attentional control and another cognitive domain (e.g., perception) in simultaneous bilinguals or recruit trilinguals to assess whether speaking more than two languages would further enhance attentional control.
References
Berken, J. A., Gracco, V. LI ., & Klein, D. (2017). Early bilingualism, language attainment, and brain development. Neuropsychologia, 98, 220–227. https://doi.org/10.1016/j.neuropsychologia.2016.08.031
Brito, N. H., Murphy, E. R., Vaidya, C., & Barr, R. (2015). Do bilingual advantages in attentional control influence memory encoding during a divided attention task? Bilingualism: Language and Cognition, 19(3), 621–629. https://doi.org/10.1017/s1366728915000851
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