Our brain is sensitive to change, and is able to modify its structure to facilitate or reinforce new learning. This includes learning a new language, which brings with it a number of advantages and changes at the brain level. Thus, the brains of monolinguals and bilinguals are not the same.
It has long been known that our brain changes and shapes itself with each new learning or experience. This is due to brain plasticity, the ability of this structure to change with learning, which happens especially in childhood. As a result of experience, learning and sensory and cognitive stimulation, neurons are able to increase their connections with each other in a stable way.
The brain and its connections change anatomically and functionally as a product of experience and the acquisition of new skills or knowledge.
An example of this it's the study carried out in 2000, which found significant differences in the brains of London taxi drivers after memorising the streets and map of the city over 4 years of study, specifically an increase in the hippocampus.
But what happens in the brains of bilingual people, how does this learning affect them, and what differences are there compared to monolinguals?
Bilinguals and monolinguals have differences when speaking their mother tongue, but not when listening to it. When speaking, monolinguals make more effective use of typical language areas, which is complemented by the use of other brain areas. On the other hand, bilinguals, because they are constantly switching languages, are more trained in the executive functions required to adapt to different tasks.
Among the advantages associated with a bilingual brain are: greater density of grey matter (where most neurons and synapses are located), greater brain activity when engaging a second language, and the delay in the onset of dementia or diseases such as Alzheimer.
There are also differences depending on whether the second language is acquired in childhood or in adulthood. In childhood, brain plasticity is greater as the brain is still developing, so learning is easier. Language in adults is lateralised in the left hemisphere, whereas children use both hemispheres in language acquisition.
In children it promotes the development of working memory (necessary for mental arithmetic or reading skills). A recent study showed that although bilingual children made more errors and had longer reaction times in a cross language test, effort and attention to switch triggered more activity in and strenghtened the dorsolateral prefrontal cortex. This area is responsible for executive function, problem solving, switching tasks and focusing while filtering irrelevant info.
In adults, it favours the development of the areas responsible for performance and attention, as well as brain health.
We can conclude that, despite not having learned a second language as a child, it is never too late to start learning it, and what better opportunity than volunteering in a foreign country!