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The Cognitive Benefits of Bilingualism/Biliteracy
by John De Mado


Prior to 1960, it was believed that the nature of the brain and its functions were fixed and were strictly a byproduct of genetics. The watershed research of Dr. Marion Diamond, Professor of Anatomy at the University of California Berkeley, challenged this thinking in 1964 when she introduced her theory of 'brain plasticity'. This theory stated that anything done to enrich the human brain, at any age, enriches the cerebral cortex, thus increasing learning capacity. Furthermore, she outlined 5 broad areas in the human experience that are essential to developing a better brain: diet, exercise, challenge, newness and love. Conversely, anything that impoverishes the human brain diminishes learning capacity.[1][2][3]

The third of the Diamond's areas, challenge, will serve as the focus of this white paper. 

Since the early 1960s, an ever growing body of research has come forth indicating that bilingualism can be of great personal advantage. Prior to that time, however, the general consensus among researchers was quite the contrary, posturing bilingualism as a handicap that atrophied linguistic and cognitive development in children. In comparison to their monolingual counterparts, the prediction was that bilingual children would inevitably have smaller overall vocabularies, would never achieve full competency in either language and would generally exhibit reduced cognitive abilities[4]. Although it is now widely accepted that bilingual children tend to own smaller overall vocabularies initially, this distinction generally remediates by age 5, with bilingual children demonstrating more robust vocabularies than their monolingual counterparts.[5]

Maria Polinsky, Professor of Linguistics at Harvard University, notes that the preeminence of monolingualism over the years has been significantly underwritten by the economic reach and geographical mass of countries such as China (Mandarin), Russia (Russian) and the United States (English), with bilingualism viewed as the exception and not the rule. Yet, according to Professor Polinsky, it is actually monolingualism that is the "aberration", with the majority of the other smaller world states being bilingual. (Please see Figure 1.) [6] Statistically, in fact, 66% of the world's children are presently being raised bilingually.[7]

Figure 1[6]

The largely flawed research models employed prior to the 1960s were also responsible for the emergent negative attitudes toward bilingualism. Influencing factors, such as socioeconomic status (SES), gender and age were largely disregarded as monolingual and bilingual study participants were compared as a group but not matched based on the aforementioned influencing factors . Once factors such as SES, gender and age were eventually systematically applied to the research studies, findings were virtually reversed, with bilinguals enjoying significant advantage over monolinguals, not only in verbal and non-verbal assessments, but in those that highlighted mental flexibility as well.[8]


It is important to note that both languages are constantly operating within the bilingual brain. As a result, these languages are continually battling one another for preeminence, creating a 'challenge' for the human brain and causing what is referred to as 'linguistic interference'. The consequences are particularly apparent when one of the two languages owned is clearly dominant over the other. Delivering or comprehending a message in Language A can be a daunting task if Language B is always interfering. This creates a need, in the bilingual brain, to control (inhibit) the amount and variety of language accessed in any given circumstance. In order to hit a balance, the bilingual brain counts on what is referred to as its 'executive functions'.[9]

The executive functions are a set of cognitive regulatory processes housed primarily, but not exclusively, in the prefrontal cortex of the brain. These processes help to select, monitor and control human behavior based on situations and personally selected goals. Among those processes are problem solving, mental flexibility, attention control, inhibitory control and the ability to task switch on the fly.

It is important to note that executive functions develop gradually over the entire human lifespan and can be affected negatively, as well, due to any confluence of events such as neurological and/or psychiatric disorders.

In order to more fully understand executive functions, definition of the various processes might be in order:

  • Problem Solving: The ability to resolve issues by employing more complex thinking.
  • Mental Flexibility: The ability to adapt cognitively to circumstances.
  • Attention Control: The ability to focus intently on critical factors.
  • Inhibitory Control: The ability to initially disregard factors that are not of immediate importance.
  • Task Switching: The ability to spontaneously and simultaneously manage tasks and situations.

Moreover, each time a bilingual speaks (output) or listens (input), these processes are automatically stimulated and triggered, causing mental challenge, thus rendering the respective areas of the brain more robust. As a result, the research notes that bilinguals are generally more adept at tasks that require conflict resolution (Problem Solving). What one does with the brain, impacts the brain both in its function and in its composition.

Bilinguals also appear to be more adept than their monolingual counterparts at switching tasks. This skill is largely derived from the constant need for bilinguals to ignore competing perceptual information (Inhibitory Control) in favor of the more relevant details dictated by the situation or context (Attention Control). Furthermore, bilinguals appear to move from task to task more rapidly (Mental Flexibility), signifying better cognitive control in general. Needless to say, these characteristics exert an overwhelmingly positive influence on academic learning, learning in general and employment opportunity in the United States as well as around the world.

It is important to note that the cognitive benefits of bilingualism may be enjoyed throughout life, not only for those raised bilingually, but even for those attempting to acquire a second language later in life. Those benefits include enriched cognitive control, neural enhancement, increased social interaction across cultures and improved metalinguistic awareness (manipulating language systems). It is precisely this improvement in metalinguistic awareness that enhances understanding of language systems and fosters better comprehension of what is heard, read and viewed. In other words, we find that literacy is a direct outcome of enriched language and not the contrary.

Bilinguals generally outperform their monolingual counterparts, not only in spoken language, but in assessments of reading ability as well.[10][11][12][13]


A preponderance of the research, both past and present, still tends to focus upon the impact of bilingualism in early childhood. Nevertheless, there is growing interest regarding the effects that bilingualism has upon the aging process. As humans beings age, there is a gradual and natural decline in cognitive prowess. In its most extreme state, this decline can manifest itself in the form of dementia or Alzheimer's Disease, with the individual eventually losing all perception of self; thecognitive reserve being virtually depleted.[14][15] As stated by Dr. Marion Diamond, "Take away the brain, you take away the person."

The term 'cognitive reserve' pertains to the sum total of cognitive processes and executive functions each individual maintains within the brain. As it relates to human existence, it is clearly imperative to maintain that reserve for as long as possible, thus forestalling the onset of general cognitive decline. Although bilingualism will not serve as a permanent hedge against dementia or Alzheimer's Disease, research shows that, on balance, bilinguals who fall victim to such cognitive disorders experience their first symptoms 5.1 years later than their monolingual counterparts and are diagnosed 4.3 years later. (Please see Figure 2.) It is believed that this is the direct result of the executive functions being recurrently challenged and deployed as they work to control and manipulate two languages existing side by side in the bilingual brain. Thus, bilingualism has the capacity to modify the neural structure and activity of the aging brain, resulting in improved memory, more mental sharpness and rerouting of neural paths potentially damaged by the aging process.[16][17]

Figure 2[18]


Growing contemporary research recognizes the significant cognitive benefits that bilingualism brings to the human experience. We are now aware that the human brain is not predestined from birth, but rather adapts to circumstances throughout life. It can be enriched or impoverished at any time, thus expanding or limiting the capacity to learn.

It is now apparent that being bilingual challenges and, in effect, exercises the brain, developing it in ways never before imagined, modifying its function and its very composition. The rewards are many and varied. Among them, we can count enhanced ability to problem solve, greater mental flexibility, improved focus and attention control, heightened ability to multitask, task switch and think in more complicated ways along with enhanced reading comprehension, semantic processing of words and employment opportunity. Furthermore, bilingualism appears to  postpone the deleterious affects of cognitive disorders and cognitive decline.  

As researchers Ellen Bialystok and Kenji Hakuta remind us in their book

In Other Words, being bilingual brings much more to humanity than just functionality in two languages and appreciation for other cultures. There are vast cognitive benefits to be enjoyed and celebrated as well. This fact may be best summed up in their own words ...

"The knowledge of two languages is greater than the sum of its parts."[19]  



1.      Squire, Larry R. (March 2009). The History of Neuroscience in Autobiography Volume 6. Oxford University Press. p. 64. ISBN 9780195380101

2.      Diamond MC, Krech D, Rosenzweig MR,. The Effects of an Enriched Environment on the Histology of the Rat Cerebral Cortex, J Comp Neurol 1964;123:111-120", February 6, 2017

3.      Bennett EL, Diamond MC, Krech D, Rosenzweig MR,. Chemical and Anatomical Plasticity of the Brain, (http://sciencemag.org/content/146/3644/610), "Science 1964:146:610-619", February 6, 2017

4.      Arsenian S. (1902) Bilingualism and Mental Development: A Study of the Intelligence and the Social Background of Bilingual Children in New York City. New York: Teachers college Columbia university.

5.      Hakuta K., Diaz R. M. (1985). The Relationship Between Degree of Bilingualism and Cognitive Ability: A Critical Discussion and Some New Longitudinal Data. In Nelson K. E. Children's Language, vol.5. Erlbaum. pp. 320–344.

6.      Polinsky, Maria The Cognitive Advantages of Bilingualism. (http://serious-science.org/cognitive-advantages-of-bilingualism-2-2610) (Image accessed April 14, 2017.)

7.      Polinsky, Maria The Cognitive Advantages of Bilingualism (http://serious-science.org/cognitive-advantages-of-bilingualism-2-2610) (Accessed April 14, 2017.)

8.      Peal E.; Lambert M. (1962). The Relation of Bilingualism to Intelligence. Psychological Monographs. 75 (546): 1–23.

9.      Bialystok, Ellen; Craik, Fergus I. M.; Klein, Raymond; Viswanathan, Mythili (2004-06-01). Bilingualism, Aging, and Cognitive Control: Evidence from the Simon Task. Psychology and Aging. 19 (2): 290–303. doi:10.1037/0882-7974.19.2.290. ISSN 0882-7974. PMID 15222822. 

10.  Bialystok, Ellen; Craik, Fergus; Luk, Gigi (2008-07-01). Cognitive Control and lexical access in younger and older bilinguals. Journal of Experimental Psychology. Learning, Memory, and Cognition. 34 (4): 859–873. doi:10.1037/0278-7393.34.4.859. ISSN 0278-7393. PMID 18605874. 

11.  Costa, Albert; Hernández, Mireia; Sebastián-Gallés, Núria (2008-01-01). Bilingualism Aids Conflict Resolution: Evidence from the ANT Task. Cognition. 106 (1): 59–86. doi:10.1016/j.cognition.2006.12.013. ISSN 0010-0277. PMID 17275801. 

12.  Bialystok, Ellen; Poarch, Gregory; Luo, Lin; Craik, Fergus I. M. (2014). Effects of Bilingualism and Aging on Executive Function and Working Memory". Psychology and Aging. 29 (3): 696–705. doi:10.1037/a0037254. PMC 4274603. PMID 25244487. 

13.  Adesope O. O.; Lavin T.; Thompson, T.; Ungerleider C. (2010). A Systematic Review and Meta-analysis of the Cognitive Correlates of Bilingualism. Review of Educational Research. 80 (2): 207–245. doi:10.3102/0034654310368803.

14.  Carlson, Stephanie M.; Meltzoff, Andrew N. (2008-03-01). Bilingual Experience and Executive Functioning in Young Children. Developmental Science. 11 (2): 282–298. doi:10.1111/j.1467-7687.2008.00675.x. ISSN 1467-7687. PMC 3647884. PMID 18333982. 

15.  Kapa, Leah L.; Colombo, John (2013-07-01). Attentional Control in Early and Later Bilingual Children. Cognitive Development. 28 (3): 233–246. doi:10.1016/j.cogdev.2013.01.011. PMC 4044912. PMID 24910499

16.  Bialystok, Ellen (1988). Levels of bilingualism and levels of linguistic awareness. Developmental Psychology. 24 (4): 560. doi:10.1037/0012-1649.24.4.560. 

17.  Adesope, O. O.; Lavin, T.; Thompson, T.; Ungerleider, C. (2010). A Systematic Review and Meta-Analysis of the Cognitive Correlates of Bilingualism. Review of Educational Research. 80 (2): 207. doi:10.3102/0034654310368803

18.  Polinsky, Maria The Cognitive Advantages of Bilingualism. (http://serious-science.org/cognitive-advantages-of-bilingualism-2-2610) (Image accessed April 14, 2017.)

19.  Hakuta, Kenji; Bialystok, Ellen (1994). In Other Words: The Science and Psychology of Second Language Acquisition. New York: Basic Books. ISBN 0-465-07565-7.