Bilingualism in Cognition: The Cognitive Advantage

Collins Kariuki, Biological Sciences, Spring 2021

Figure 1: Map showing multilingual nations. Purple indicates nations that have more than one official language, green indicates nations with one official language but functionally multilingual, blue indicates nations with no official language and multiple languages in practice.

Bilingualism is defined as the continuous use of two languages. Bilingualism is a factor that influences Cognitive Reserve (CR), which protects against cognitive decline and hence the “bilingual advantage”. Recently, researchers from Spain investigated whether active bilingualism also protects against cognitive decline.

Source: Wikimedia Commons.
Author: Arkyan.

There is no clear definition of bilingualism. In its simplest definition, it refers to the continuous use of two languages (Franson, 2009; Pauls, 2019). Bilingualism is complicated to define because of its many definitive facets such as context (stages), proficiency, purpose. For instance, when considering context, there is simultaneous bilingualism where an individual is bilingual by growing up simultaneously using two languages. There is also sequential bilingualism where an individual is exposed to the second language after gaining fluency in his or her first language (Franson, 2009). Despite the complications in its definition, bilingualism serves as a crucial topic in cognition. When it comes to bilingualism research, one major objective is determining the relationship between bilingualism and brain damage, specifically, researchers are interested in how being bilingual can help mitigate cognitive decline in old age.
Previous studies on brain damage fail to provide conclusive evidence as to why some people are more susceptible to brain damage than others. For example, there is variability in susceptibility to mild cognitive impairments (MCIs), which lead to dementia and substantial decline in cognitive abilities. Among the most dangerous forms of dementia is Alzheimer’s Disease (AD). AD is the most common cause of dementia and it accounts for 60-80% of dementia cases (Mild Cognitive Impairment (MCI), n.d.; What is Alzheimer’s?, n.d.) There seemed to be a missing link connecting the degree of brain damage and its clinical outcome, hence the concept of the reserve was formulated to explain this gap in brain damage susceptibility. Reserve can be defined as the amount of damage that can be sustained before reaching a threshold for clinical expression (Stern, 2002). Even though there are many layers attached to reserve, it can be divided into two forms: brain reserve and Cognitive Reserve (CR). Brain reserve is a measure of the quantification of one’s brain size in protecting against MCIs, while CR is the brain’s ability to protect against cognitive decline (Stern, 2012; Stern, 2002). Many factors affect CR and some of them include, one’s socioeconomic status, cognitive capacity, culture, education level, immigration status, cultural traits, the variation in linguistic experiences, and interactional contexts and lastly, bilingualism (van de Noort et al., 2019). It has regularly been hypothesized that since bilingualism is a key factor that influences CR, bilinguals are thought to have a higher level of CR and hence are less susceptible to MCIs and also AD. However, some studies have failed to replicate this bilingual advantage suggesting that it might depend on the type and degree of bilingualism (Calabria et al., 2020).
A team of researchers from the Pompeu Fabra University’s Center for Brain and Cognition in Spain, lead by Marco Calabria, investigated whether active bilingualism, continuous use of two languages, may protect against cognitive decline. They collected participants, with varying proficiencies in Spanish and Catalan, and MCI and AD by considering factors such as the age of onset of the cognitive decline symptoms, age of diagnosis etc. The participants were tested on four Executive Control (EC) tasks: the Flanker task, spatial Stroop Task, Task switching and N-back task, making sure to control other CR-factors such as education level and occupation (Calabria et al., 2020). These tasks test one’s Executive Functions (EFs) – high-level cognitive processes that facilitate new ways of behaving and optimise one’s approach to unfamiliar circumstances (Understood Team, n.d.).

Although Calabria and his colleagues again proved that bilingualism was a significant factor in boosting CR and hence slowing down senile dementia in the case of MCIs, they could not replicate the conclusions set forth by previous researchers that bilingualism protects against the onset of AD (Calabria et al., 2020). In fact, Calabria and his team of researchers found out that there was a point at which the underlying pathology in AD is so severe that any possible cognitive (bilingual) advantage would no longer be maintained, and individuals with both high and low levels of CR would show the same cognitive decline (Calabria et al., 2020).

Calabria et al.’s study can serve as a benchmark for future bilingualism studies. Future research should investigate other cognitive impairments through bilingual research on diseases such as Parkison’s and Huntington’s which mostly affect the brain and executive functions (Calabria et al., 2020). The challenge remains in explaining the origin of such an advantage in neurodegenerative diseases. Insight into the neural basis of the cognitive reserve could produce information that would allow interventions to be better focused (Stern, 2012).

References

Mild Cognitive Impairment (MCI) | Symptoms & Treatments. (n.d.) Alzheimer’s Association. Retrieved June 2, 2021, from https://www.alz.org/alzheimers-dementia/what-is-dementia/related_conditions/mild-cognitive-impairment

What is Alzheimer’s? Alzheimer’s Disease and Dementia (n.d.). Alzheimer’s Association. Retrieved June 2, 2021, from https://alz.org/alzheimers-dementia/what-is-alzheimers

Calabria, M., Hernández, M., Cattaneo, G., Suades, A., Serra, M., Juncadella, M., Reñé, R., Sala, I., Lleó, A., Ortiz-Gil, J., Ugas, L., Ávila, A., Ruiz, I. G., Ávila, C., & Costa, A. (2020). Active bilingualism delays the onset of mild cognitive impairment. Neuropsychologia, 146, 107528. https://doi.org/10.1016/j.neuropsychologia.2020.107528

Franson, C. (2009, May 2). What is Bilingualism? https://www.naldic.org.uk/Resources/NALDIC/Initial%20Teacher%20Education/Documents/B1.pdf

Pauls, E. (2019, March 20). Bilingualism [..Com]. Britannica. https://www.britannica.com/topic/bilingualism

Stern, Y. (2002). What is cognitive reserve? Theory and research application of the reserve concept. Journal of the International Neuropsychological Society: JINS, 8(3), 448–460.

Stern, Y. (2012). Cognitive reserve in ageing and Alzheimer’s disease. The Lancet Neurology, 11(11), 1006–1012. https://doi.org/10.1016/S1474-4422(12)70191-6

Understood Team. (n.d.). What is executive function? Retrieved May 27, 2021, from https://www.understood.org/en/learning-thinking-differences/child-learning-disabilities/executive-functioning-issues/what-is-executive-function

van den Noort, M., Struys, E., Bosch, P., Jaswetz, L., Perriard, B., Yeo, S., Barisch, P., Vermeire, K., Lee, S.-H., & Lim, S. (2019). Does the Bilingual Advantage in Cognitive Control Exist and If So, What Are Its Modulating Factors? A Systematic Review. Behavioral Sciences, 9(3), 27. https://doi.org/10.3390/bs9030027