As communities continue to be more and more diverse in their populations, the number of languages present increases as well. As bilingualism becomes more common in households across the world, the benefits of such a skill of knowing more than one language has come into question.
There is a theory, typically called the “critical period hypothesis” that states that children have an easier time learning and better benefit from learning a second language in comparison to adults. This theory follows the stereotypical generalization that the left brain is the “logical and analytical” side of the brain, whereas the right brain is considered to be “emotional and creative.” Though this has been disproven and is no longer a well-held theory in psychology and neuroscience, you still see it from time to time in generalizable situations.
For example, the “critical period hypothesis” states that children get more out of learning a second language because their brains are still developing, and synaptic plasticity is at a high. This is believed to allow children to learn the language on both sides of the brain and gain an emotional component to the language, where adults are believed to lean more towards a “left-brain” understanding of the language.
This learning of a second language tends to be localized to the dorsolateral prefrontal cortex which is also highly involved in executive functioning, such as working memory and flexible thinking. The learning of a second language is believed to strengthen executive function, and in turn be a neuroprotective factor of neurogenerative diseases, such as Alzheimer’s and dementia.
Though the idea of teaching a child a second language seems like a simple “YES” answer, there is a secret hinderance that has come into the light of research. With 1.4 million individuals experiencing a mild traumatic brain injury (mTBI) on a yearly basis with most occurring in the prefrontal cortex or temporal lobes, it definitely raises the question if bilingualism still shows similar neuroprotective factors.
According to Raitu et al. (2017), a bilingual brain is just as susceptible to the impaired executive function and cognition as any monolingual brain. Even if the neurons are strengthened by the bilingual brain they still undergo immense strain following an mTBI. This strain comes from the calcium influx, axonal injury, altered neurotransmission, and vulnerability to second injury from an energy metabolism crisis. Specifically, axonal injury and altered neurotransmission is believed to be at the root of impaired cognition and executive function following an mTBI.
Besides being just as susceptible to executive function deficits, bilinguals are also at an increase risk of language control deficits following a mTBI. One theory states that following a mTBI, languages return in a disproportionate manner with the one most frequently used at time of impact returns faster. Monolinguals sustaining one mTBI have not been mentioned to experience such a deficit.
This language control deficit coming from axonal injury raises a concern from the lack of myelination seen in younger children. Myelination offers a “cushion” to the axon, and a decreased volume of myelin on any neuronal axon can significantly impact the results of an mTBI.
To put it all together, if a child learns a second language during the critical period of development, it can significantly benefit them in the long run. However, they are at an increased risk of executive function and language control deficits after sustaining an mTBI, or concussion, due to lack of myelination on axons in their developing brain. This can impact the recovery time and “Return to Play/Learn”. This is not meant to discourage bilingualism, but to show how important it is to take head injuries seriously in children with their developing brain.
Photo Sourced From: https://mosaicscience.com/bilingual-brains/
