Bilingualism and the Brain

Alice Hofsetz -

Introduction

Shaina Shetty, a woman born in Detroit, spoke Tulu (an Indian language with only 1.7 million speakers) up until she started elementary school in Detroit:

“[My parents] had to immerse me in English… They didn’t want to confuse me… We ended up speaking English all the time,” Shetty explained [1].

Shetty’s experience represents one of the main misconceptions about bilingualism in children throughout the U.S. One such misunderstanding is that bilingualism can cause delayed speech problems in children exposed to two languages [2]. In addition, children who know their native language but have not yet learned English, also known as English as a Second Language (ESL) students, are often encouraged to fully immerse themselves in the English language while avoiding speaking their native language until they develop a basic understanding of English. This is called the “hold-back” approach to language-learning, in which full English immersion, both at school and at home, means children receive little exposure to their native language, often resulting in the loss of the ability to speak that language. Shetty’s experience shows how this approach can cause children to lose the ability to speak in their native language [2]. While the hold-back approach is a common strategy for children to learn English, it can also be frustrating, and data suggests that it is not the best method to help ESL students. Comparing standardized tests across racial or ethnic groups can provide insight into the effectiveness of different educational approaches. A study released in 2008 showed that states with a bilingual education approach had smaller achievement gaps (a measure of when one racial or ethnic group does significantly better on these standardized tests than another) when compared to states with English-only education [3]. One teacher in Arizona, Sandoval-Taylor, voiced her frustration about being barred from helping ESL students using their native language:

“Even though I knew their primary language and could help them with that tool, I instead had to use English only,” Sandoval-Taylor stated [3].

Inspired by evidence-based research on bilingual-driven education, many schools have recently been making conscious efforts to incorporate teaching foreign languages into their curriculum [3]. For instance, in the past few years, states have repealed “English-only” laws that banned bilingual education in some districts or otherwise restricted dual-language programs so only students proficient in English could enroll [3]. These laws perpetuated the myth that learning more than one language can be confusing and detrimental to a child. 

In the next couple of sections, we will explore how educational neuroscience and studies on bilingual and monolingual people can help guide the future of education in the US. First, we will learn about educational neuroscience, then we will connect it to the plethora of research about the cognitive benefits of speaking multiple languages, and finally, we will look at the potential future of multilingual education. There are many cultural and societal benefits of bilingualism, such as improving communication and preserving a culture throughout generations, but this article will focus primarily on the effects of bilingualism on the brain.

What Can Neuroscience Tell Us About Education?

A field of study called educational neuroscience combines cognitive neuroscience, psychology, and modern technology to understand how human knowledge develops throughout one’s lifespan [2]. Evidence from educational neuroscience research aids teachers and school administrators in making decisions for the benefit of their students. 

Educational neuroscience may be able to answer the fundamental question of when the best time is to teach a child a second language. In 2009, Dr. Laura-Ann Petitto led a study that examined how the age of language acquisition affects the brain [2]. First, participants were split into two main groups: one exposed to two languages before age five and the second exposed to two languages after age five. The researchers used two types of brain scanning technologies, functional Magnetic Resonance Imaging (fMRI) and functional Near Infrared Spectroscopy (fNIRS), to examine the neural activity in the brains of monolinguals and bilinguals while completing language tasks. fMRIs use a magnetic field to measure blood flow to different areas of the brain, indicating the parts of the brain are active during the task. Alternatively, fNIRSs use near-infrared light to measure changes in oxygen density to determine neural activity. Together, fMRIs and fNIRSs can be used to learn about language organization in the brain [2]. 

The researchers found that bilinguals exposed to two languages before the age of five use overlapping language areas within the left hemisphere of the brain to understand each language, similar to monolinguals. In other words, these bilinguals use similar brain regions to integrate both languages, rather than separating the two. The overlapping language areas in the brain included Broca’s area, the superior temporal gyrus (STG), and the left inferior frontal gyrus (LIFC) [2]. Broca’s area, a region of the brain in the LIFC, is involved in speech production, speech comprehension, and working memory [4]. The STG includes the Wernicke’s area and is involved in auditory processing. A good way to remember the difference between Broca’s area and Wernicke’s area is by thinking about what happens when there is damage to one of those areas, also known as aphasia. Broca’s aphasia results in difficulty making speech sounds or the physical act of talking, while Wernicke’s aphasia results in difficulty understanding speech [5]. For example, a person with Broca’s aphasia may be able to understand language, but unable to respond to others in a way that makes sense, while a person with Wernicke’s aphasia may be able to speak in coherent sentences but not understand what others are saying. Lastly, the LIFC is involved in the unification of stored language information in the frontal lobe to spoken phrases and sentences [6].

In the study described above, bilingual adults exposed to two languages after age five were found to have increased bilateral activation and use of their frontal lobe tissue, and exert more mental effort to complete language tasks [2]. On the other hand, bilinguals exposed to two languages after age five showed minimal bilateral frontal lobe activation. So, children who learned a second language before age five had similar language organization in the brain compared to monolinguals, but children who learned a second language later on had atypical neural organization for language. It is important to note that this study primarily focused on Spanish-English bilinguals, so it may be useful to study the impacts of different language pairs to see if bilingualism has similar effects on the brain [2].

Why do these differences occur, and why was “five years old” the cutoff for this study? One possible explanation is that the time period between birth and five years of age is considered a critical period of language acquisition [2]. A critical period is a time in life when experiences have long-lasting effects on the cognitive functioning of an individual, like in early childhood or early adolescence. A defining feature of a critical period is high brain plasticity, when the brain can make or alter connections between neurons more easily as a result of lived experiences [7]. The brain codes newly learned information through these changes in connections, leading to an increased ability to alter connections between neurons to facilitate learning [8]. In early childhood, there is an abundance of neuronal connections that are dynamically made and shifted around which helps facilitate the learning of new languages. These windows of plasticity are a result of evolution; they occur at staggered times to optimize the acquisition of important functions like language [9]. When these high periods of brain plasticity occur at the same time as significant environmental input, like language, typical brain development required for higher-order functions can occur. Critical periods are even present in other animals, like barn owls, geese, and songbirds — birds actually have an optimal time period to learn vocal behavior, just like us [9]! 

Now, although the “divider” for this study was five years of age, that age is simply an estimate, not a hard-and-fast rule. In general, language proficiency correlates negatively with age of acquisition, meaning the older an individual is when they learn a new language, the lower their future proficiency in that language [10]. This makes intuitive sense, and many people are painfully aware of this connection: those who learn a new language after childhood may notice that the amount of effort they must put into it is much greater than a kindergartener learning the same language. Again, this is because once the childhood period of high neural plasticity ends, synaptic density and metabolism levels in the brain decrease accordingly, making it more difficult to learn a new language [11]. Related to this are the changes in grey matter and white matter ratios of the brain throughout life [12]. Grey matter is mostly composed of cell bodies of neurons and unmyelinated neurons, whereas white matter is made up of the myelinated, or insulated, neuron. Myelin is a fatty substance that insulates some neurons, allowing information in the form of electrical signals to move through the axon at a faster rate. Higher grey matter levels signify greater branching of axons and higher levels of shifting neuronal connections. When white matter levels are higher than grey matter levels, more energy is being devoted to adding myelin to axons to strengthen connections between neurons than making and breaking new connections. In early childhood, grey matter density increases, but in adolescence, grey matter density decreases as neuronal connections are purged in a process called “pruning”. Pruning may sound like a bad thing, but it’s really not! During pruning, unused connections are lost and relevant connections are strengthened. So, the connections that are used frequently are strengthened, leading the way for the adult version of the brain [12]. But, if you decide to learn a language after pruning has already happened, the new connections are more difficult to make [11].

If language-learning is easier in early childhood, why do most schools in the US introduce foreign languages much later when students are in high school? Well, the “hold-back” approach to language-learning remains ingrained in the US school system as an artifact of a time when many believed bilingualism to cause confusion in young children. It may have been related to the “English-only movement” designed to limit the use of other languages. The sentiments that allowed anti-bilingualism laws to pass in the first place still exist, and it can be damaging to students psychologically and linguistically [13]. Culture and language are deeply intertwined, and limiting the use of a student’s native language in school can push them further away from their culture. English-only policies stem from racist methods of assimilation for Native American children, as well as refugee and immigrant children. It also doesn’t work: children who learn to read in their native language learn to read in a second language more quickly than those who first learn to read in their second language [13]. By allowing students to speak in their native language and including dual-language programs in schools, educators can begin to move away from the harmful methods of English-only policies.

Educational neuroscience can inform teachers and school administrators about when it is best to teach students a second language to maximize their future proficiency in that language – which would be as early as possible in their education, even starting as early as preschool or kindergarten and going through high school. But what is the point of teaching kids a second language? The next section will explain some of the cognitive benefits of knowing more than one language.

The Cognitive Benefits of Bilingualism (Or Multilingualism)

So, what’s the point of bilingualism? Why not stick to one language?

Multilingualism is associated with many cognitive benefits, such as improved working memory, better abstract representation skills, and delayed onset of Alzheimer’s disease [14]. Alzheimer’s disease (AD) is a progressive neurodegenerative disorder that results in issues with memory and behavior. AD affects millions of Americans, and 1 in 3 seniors die with Alzheimer’s or another form of dementia [14]. The exact causes of AD, and thus possible treatments, are still being studied, but there are some genetic markers and lifestyle choices that increase an individual’s risk of AD [16]. Lifelong bilingualism has been shown to delay the onset of clinical AD by about four years, comparable to the effects of physical fitness and not smoking [17]. This may occur through the strengthening of executive control (EC) circuits. Executive functions, controlled by EC circuits in the brain, help to control behavior such as planning and attention and are typically associated with the prefrontal lobe of the brain. EC functions decline with age and brain diseases like Alzheimer’s. When researchers compared older adult bilinguals and monolinguals, the bilingual group had stronger resting connectivity in the cerebral cortex and better white matter integrity in tracts involved in EC circuits. Notably, the cerebral cortex is involved in higher-order thinking (memory and language) as well as sensory information. They also showed that monolinguals had steeper declines in EC functions with age and were slower with EC tasks than bilinguals [17]. 

Being multilingual positively affects the structure of the brain. Specifically, it affects the structural reorganization of the brain [10]. A study done on 25 monolinguals, 25 early bilinguals, and 33 late bilinguals showed that bilinguals and individuals who are learning a second language have an increased density of grey matter in their left inferior parietal cortex, a region in the parietal (sensory) lobe that is activated in verbal-fluency tasks. The grey matter densities were measured using voxel-based morphometry (VBM), a technique that uses MRI to calculate structural differences between groups. Researchers also noticed a significantly increased density of grey matter in the right hemisphere, as well as a notable increase in the left. These effects were pronounced in bilinguals who learned a second language earlier in life, suggesting that grey matter density in a region correlates negatively with age of bilingual acquisition [10]. These findings regarding structural changes in the brain and age of bilingual acquisition mirror the findings discussed earlier in which language proficiency correlates negatively with age of acquisition. 

Bilinguals also tend to have more connected sub-networks in the brain than monolinguals [18]. Sub-networks are highly-connected regions in the brain, and examining them provides information about the organization of the brain as a whole. One study compared sub-networks by using the Diffusion Tensor Imaging, or DTI, technique, which uses MRI imaging to determine anatomical connectivity. Two structural sub-networks in particular have been found to be more connected by white matter tracts: one sub-network involving the left frontal, parietal, and temporal areas and another involving the left occipital, parietal, and temporal regions as well as the right superior frontal gyrus, all of which are implicated in language processing. Thus, bilinguals use specific sub-networks to facilitate the learning and use of two languages, and these highly connected sub-networks may be a reason why bilinguals tend to be better at general EC tasks than monolinguals, such as switching between tasks [17][18]. 

Thus, it is clear that bilingualism benefits the structure and function of the brain: it is associated with higher grey matter densities in many regions of the brain and helps with executive control tasks. How can these data altogether guide the future of education?

The Future of Education Through the Lens of Neuroscience

Educational neuroscience tells us that bilingualism provides a multitude of cognitive benefits, and that it is best to learn new languages earlier in life to maximize proficiency. One possible way of utilizing this information in education is teaching children a second language in elementary school by immersing them in that language through an immersion program [19]. Students who study abroad often partake in immersion programs as they gain exposure to a different culture and language. Immersion programs are founded on the idea that when a different language or culture surrounds a person, they can pick up on a certain language or cultural information more proficiently. In many immersion programs in elementary schools, some classes are taught in the children’s native language and others are taught in a secondary language that the children are still learning [19]. Right off the bat, this seems like the perfect way to merge the studies we looked into earlier with education: it combines early bilingual teaching with immersive, continuous contact with the secondary language. Before we decide to implement immersion programs in every US school district, we need to look at the data from immersion programs. Like most decisions in the field of education, there are pros and cons to school immersion programs. 

French immersion programs in Canadian public education presented their academic curriculum entirely in French, and the children practiced no French at home [20]. The study showed improved English language proficiency when English-speaking children in grades two to five were educated using a French immersion program compared to their monolingual counterparts. However, the French vocabulary and proficiency of the students increased at a slower rate compared to the students’ English vocabulary and proficiency [20]. Related to this, other studies on French immersion programs show that French language and literary scores are lower in children whose home language is English when compared to monolingual French children [21]. This suggests that bilingual education in schools may not be as effective as bilingualism in the home to develop proficiency in a second language.

A study on elementary school children looked at the differences between monolingual German schools and bilingual German-English immersion schools [22]. The study aimed to understand how educational bilingualism, or a second language taught through a school program, relates to cognitive outcomes in children. The children in the monolingual school had two 45-minute-long English lessons each week starting in grade 3, while the bilingual school had over 70% of lessons taught in English in all grades. The children were tested at the end of grade 3 and the end of grade 4. The study found that the children in bilingual programs outperformed the children in monolingual programs on cognitive tasks involving working memory and phonological awareness in grade 4, but in grade 3, bilinguals only had an advantage in phonological awareness. Cognitive and linguistic benefits were present in bilingual children regardless of socioeconomic status, suggesting that bilingual education may be a way to limit the possible negative cognitive effects of low socioeconomic backgrounds. This study, along with another looking at Belgian children in French-English immersion schools that found three years in bilingual education was sufficient for cognitive benefits, suggest that prolonged partial immersion programs may be the most beneficial for young students [22][23].

Although many immersion programs in schools are successful, there are some social issues. Some critics claim that French immersion programs in Canada are elitist because low-achieving students are discouraged from entering French immersion classrooms [24]. Another concern in many school districts is that wealthier families or families in wealthier school districts may have greater access to immersion schools than poorer families, pointing to a major equity issue [24]. 

Studies have shown that immersion programs can be successful, and educational neuroscience studies show that the “hold-back” technique to language-learning is not productive. By dispelling myths that still prevail throughout the country, parents and teachers alike may be more encouraging of bilingualism in children, and school administrators may even consider implementing bilingual immersion programs in their schools. 

Shetty, the woman introduced in the beginning of the article, was affected by the “hold-back” approach: when she started school, she was able to speak Tulu, but she slowly lost her ability to speak it through the years [1]. Now, although she can understand it, she cannot speak in Tulu with her parents or grandparents, making her part of the last generation of her family that can speak the language:

“I think it’s a little heartbreaking for [my parents]. Especially given that realistically I probably won’t end up marrying someone who also speaks this language, so this will probably be our family’s last generation that does” [1].

Perhaps if Shetty was not encouraged to speak “English-only,” she would have a stronger connection to the Tulu language and her family’s culture. The future of education may very well be widespread bilingual education.

References

  1. Prasad, R. (2017). "Living as a first-generation Indian immigrant who can't speak her native language." Brown Girl Magazine. https://browngirlmagazine.com/2017/10/living-indian-immigrant-who-cant-speak-native-language/ 
  2. Petitto, L. A. (2009). New discoveries from the bilingual brain and mind across the life span: Implications for education. Mind, Brain, and Education, 3(4), 185-197. https://doi.org/10.1111/j.1751-228X.2009.01069.x
  3. Mitchell, C. (2019). "'English-only' laws in education on verge of extinction." Education Week. https://www.edweek.org/teaching-learning/english-only-laws-in-education-on-verge-of-extinction/2019/10 
  4. Friederici, A. D. (2011). The brain basis of language processing: From structure to function. Physiological Reviews, 91(4), 1357–1392. https://doi.org/10.1152/physrev.00006.2011 
  5. Guy-Evans, O. (2021). Wernicke's area location and function. Wernicke's Area Location and Function. Simply Psychology. https://www.simplypsychology.org/wernickes-area.html 
  6. Li Y., Seger C., Chen Q., & Mo L. (2020). Left Inferior Frontal Gyrus Integrates Multisensory Information in Category Learning. Cerebral Cortex. doi: 10.1093/cercor/bhaa029. 
  7. Gervain J. Plasticity in early language acquisition: the effects of prenatal and early childhood experience. Current Opinion in Neurobiology. (2015) 35:13-20. doi: 10.1016/j.conb.2015.05.004.
  8. Trafton, A. (2015). Neuroscientists reveal how the brain can enhance connections. MIT News, Massachusetts Institute of Technology. https://news.mit.edu/2015/brain-strengthen-connections-between-neurons-1118#:~:text=When%20the%20brain%20forms%20memories%20or%20learns%20a,the%20strengthening%20of%20these%20connections%2C%20also%20called%20synapses.?msclkid=e8ff19ebcf4411ec9b81e9d05f802799 
  9. Reh, R. K., Dias, B. G., Nelson, C. A., 3rd, Kaufer, D., Werker, J. F., Kolb, B., Levine, J. D., & Hensch, T. K. (2020). Critical period regulation across multiple timescales. Proceedings of the National Academy of Sciences of the United States of America, 117(38), 23242–23251. https://doi.org/10.1073/pnas.1820836117
  10. Mechelli, A., Crinion, J. T., Noppeney, U., O'Doherty, J., Ashburner, J., Frackowiak, R. S., & Price, C. J. (2004). Neurolinguistics: structural plasticity in the bilingual brain. Nature, 431(7010), 757. https://doi.org/10.1038/431757a
  11. White, E. J., Hutka, S. A., Williams, L. J., & Moreno, S. (2013). Learning, neural plasticity and sensitive periods: implications for language acquisition, music training and transfer across the lifespan. Frontiers in systems neuroscience, 7, 90. https://doi.org/10.3389/fnsys.2013.00090
  12. Bryck, R. L., & Fisher, P. A. (2012). Training the brain: practical applications of neural plasticity from the intersection of cognitive neuroscience, developmental psychology, and prevention science. The American psychologist, 67(2), 87–100. https://doi.org/10.1037/a0024657
  13.  Efron, K. (2019). The dangers of "English-only" policies (for ESL students) in school. Ethical ESOL. https://www.ethicalesol.org/blog/hhryxasqrobl9b8gzcza24aj6x5w5q 
  14. Goldenberg, C., & Wagner, K. (2015). Bilingual education: Reviving an American tradition. American Educator, 39(3), 28.
  15. "Alzheimer's disease facts and figures." Alzheimer's Disease and Dementia. https://www.alz.org/alzheimers-dementia/facts-figures 
  16. Herrup, K. (2021). "How not to study a disease: The story of Alzheimer's." The MIT Press. 
  17. Gold B. T. (2015). Lifelong bilingualism and neural reserve against Alzheimer's disease: a review of findings and potential mechanisms. Behavioural brain research, 281, 9–15. https://doi.org/10.1016/j.bbr.2014.12.006
  18. García-Pentón, L., Pérez Fernández, A., Iturria-Medina, Y., Gillon-Dowens, M., & Carreiras, M. (2014). Anatomical connectivity changes in the bilingual brain. NeuroImage, 84, 495–504. https://doi.org/10.1016/j.neuroimage.2013.08.064
  19. Barbu, C., Gonzalez, A., Gillet, S., & Poncelet, M. (2019). Cognitive Advantage in Children Enrolled in a Second-Language Immersion Elementary School Program for One Year. Psychologica Belgica, 59(1), 416–435. https://doi.org/10.5334/pb.469
  20. Hermanto, N., Moreno, S., & Bialystok, E. (2012). Linguistic and metalinguistic outcomes of intense immersion education: How bilingual?. International journal of bilingual education and bilingualism, 15(2), 131–145. https://doi.org/10.1080/13670050.2011.652591
  21. MacKay, E., Chen, X., & Deacon, S. H. (2023). Longitudinal predictors of French word reading difficulties among French Immersion children. Annals of dyslexia, 73(1), 73–89. https://doi.org/10.1007/s11881-022-00275-z 
  22. Trebits, A., Koch, M. J., Ponto, K., Bruhn, A. C., Adler, M., & Kersten, K. (2022). Cognitive gains and socioeconomic status in early second language acquisition in immersion and EFL learning settings. International Journal of Bilingual Education and Bilingualism, 1-14. https://doi.org/10.1080/13670050.2021.1943307 
  23. Nicolay, C., & Poncelet, M. (2015). Cognitive benefits in children enrolled in an early bilingual immersion school: A follow up study. Bilingualism: Language and Cognition, 18(4), 789-795. doi:10.1017/S1366728914000868.
  24. Delcourt, L. (2018). Elitist, inequitable and exclusionary practices: A problem within Ontario French immersion programs? A literature review. In Actes du Symposium JEAN-PAUL DIONNE Symposium Proceedings. 2(1). 7-26.