Over the past several years, there has been an increased research output in the field of language acquisition and its effects on the brain. This is especially true with regards to the effects of bilingualism.
Language acquisition has been shown to impact neuroplasticity. Neuroplasticity is the ability of the brain to undergo structural changes in response to stimulus, behavioral experience, or cognitive demands. The link between neuroplasticity and language acquisition has been documented in the literature; evidence suggests that as a product of learning a language and utilizing several languages, changes in brain anatomy are induced. These changes include the pattern of functional neurons and can occur rapidly and at any age.
The benefits of a bilingual brain - Mia Nacamulli
A study conducted in 2012 measured structural changes in the prefrontal and temporal cortices, particularly looking at changes in grey matter density. Grey matter is comprised of the cell bodies of neurons, and this area is generally associated with intelligence, attention, memory, and language processing. This contrasts with the white matter, which comprises axon bundles carrying nerve impulses between neurons and predominantly serves to connect different regions of grey matter; it consequently determines the speed of information processing and memory recall.
Participants underwent an intensive course of German and were examined at the beginning of the stay and approximately five months later. Researchers demonstrated that participants underwent an increase in the grey matter, which did not correlate with the degree of language proficiency. This indicated that this effect was directly attributable to second language acquisition.
A similar study conducted in 2012 observed that cortical thickness on the volume of the hippocampus was also increased in response to second language exposure. Collectively, these studies concluded that language acquisition could increase the density of grey matter.
In an investigation of the effect of early language exposure on the brain, researchers compared Spanish Catalan bilinguals exposed to two languages throughout that development, and a group cohort matched Spanish monolinguals. The bilingual group works left to have a larger Heschel's gyri relative to monolinguals, an indication of a greater size of the auditory cortex. The researchers concluded that second language learning is a causal factor in the increased size of the auditory cortex.
The Effect of Language Learning on Aging
Recent evidence has suggested that there is a positive impact of bilingualism on cognition - with a later onset of dementia. Researchers from the University of Edinburgh used the Lothian Birth Cohort 1936 to address wasn't learning a second language can influence later cognitive performance. Disco halt offered the opportunity to address confounding variables such as ethnic and environmental differences.
The researchers found that bilinguals performed significantly better on tests conducted between 2008 and 2010. The strongest effects were observed on general intelligence and reading. Overall results suggested a positive effect of bilingualism on cognition in older age and this included those who acquired a second language as adults.
The bilingual executive advantage (BEA) hypothesis, that is, the improvement in cognitive functions, specifically executive functions, results from the ability to control more than one language system. This theory is controversial, and a recent systematic review, including 53 studies, does not apply to working memory. There is evidence to support the bilingual effect in relation to cognitive flexibility. However, the inconsistent results found across studies prevent clear conclusions from being drawn; further studies are still needed.
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The Impact of an Additional Language on Working Memory
Working memory is defined as a dedicated, mental workspace for the storage, processing, and manipulation of information. One aspect of working memory includes the holding of information in a speech-based format, called the phonological loop.
Bilinguals have been shown to outperform individuals who can only speak one language in tasks that require working memory. The response rate amongst those who can speak more than one language was more accurate in response to trials, which suggests that bilinguals have an advantage in executive functioning.
Bilingual participants could also outperform monolinguals in tests that required areas of the brain unrelated to the processing of language. This included visual-spatial span, suggesting that language acquisition can improve working memory beyond language processing.
The Impact of an Additional Language on Verbal Intelligence
Peal and Lambert published a paper in 1962 that was considered a hallmark study highlighting the importance of controlling for several variables such as socioeconomic status, sex, and age, as well as underscoring the importance of standardized measures for bilingualism when selecting populations to be studied. In this particular study, in a comparison between bilingual and monolingual participants, bilinguals performed better than monolingual counterparts in both verbal and nonverbal tests, however, the difference was more pronounced in non-verbal testing.
The advantage conferred by bilingualism is thought to be a result of greater mental flexibility and the ability to form concepts.
The Impact of an Additional Language on Nonverbal Intelligence
Non-verbal intelligence is defined as a set of cognitive and problem-solving skills as applied to tasks that don't require the use of language. Examples of nonverbal tasks include reasoning, the recognition of visual sequences, the ability to understand visual information, the ability to conceive abstract ideas, and the ability to recognize visual cues in social contexts i.e., body language.
According to Maria Viorica, the pioneer of the notion of coactivation in those with bilingualism, bilingual spoken language understanding confers the ability to activate inhibitory regulation in the prefrontal cortex. This is because this area of the brain must select between 2 languages that are co-activated, that is, able to be spoken concurrently. As a result, the bilingual brain it's subject to continuous exercise and is, therefore, more capable of executing cognitive tasks as a result of having better control of this area of the brain.
However, a more recent study conducted in 2019 suggests that there are no major differences between bilingual and monolingual matched participants in nonverbal switching and suggests that bilinguals may not have better cognitive control than monolinguals.
The impact of speaking an additional language has several positive cognitive effects, with wide implications on a range of disciplines - including human brain health. Several studies have suggested bilingualism can improve their brain's cognitive function, producing great cognitive control abilities, increased nonverbal and verbal capabilities, increased perceptual sensitivity, and confers some protection against aging, most notably delaying the onset of dementia.
References:
- Li P, Jeong H. (2020) The social brain of language: grounding second language learning in social interaction. Nature. doi:10.1038/s41539-020-0068-7.
- Friesen DC, Bialystok E. Metalinguistic Ability in Bilingual Children: The Role of Executive Control. (2012) Riv Psicolinguist Appl.
- Bak TH, Nissan JJ, Allerhand MM, Deary IJ. (2014) Does bilingualism influence cognitive aging?. Ann Neurol. doi:10.1002/ana.24158.
- Mårtensson J, Eriksson J, Bodammer NC, et al. (2012) Growth of language-related brain areas after foreign language learning. Neuroimage. doi: 10.1016/j.neuroimage.2012.06.043.
- Bialystok E, Craik FI, Luk G. (2012) Bilingualism: consequences for mind and brain. Trends Cogn Sci. doi:10.1016/j.tics.2012.03.001.
- Pliatsikas C, Pereira Soares SM, Voits T, et al. (2021) Bilingualism is a long-term cognitively challenging experience that modulates metabolite concentrations in the healthy brain. Sci doi:10.1038/s41598-021-86443-4
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