This is a very interesting TEDx Talk about the “benefits of a bilingual brain” by Mia Nacamulli. – I only would like to point out that grown ups usually learn a new language in a very “conventional” way, which is rule-based (i.e. using books, learning grammar first), what leads to using one side of the brain only, like it is mentioned in this film/talk.
When adults learn a new language in the same spontaneous, memory based way like children, the brain activity is similar to the one of children who acquire a new language by involving both hemispheres. The approach is then less “rational” and more “emotional”. Language ability is measured in two parts: the active part – speaking and writing – and the more receptive part – listening and reading.
A balanced bilingual has a nearly equal ability in both (or all) the languages, whereas most bilinguals use their languages in “various proportions, and depending on their situation, and how they acquired each language they can be classified into three general types”*:
They learn the two languages, two linguistic codes, simultaneously in the same context where they are used concurrently, so that there is a fused representation of the languages in the brain. – This is the case when a child is brought up by bilingual parents, or parents with two different linguistic backgrounds.
The person learns the languages in separate environments, and “works with two sets of concepts”, and words of the two languages are kept separate with each word having its own specific meaning. This happens for example when a child attends daycare or preschool in an additional language.
The person attained her bilingualism later in life. As a result, she often uses her primary language to subordinate the second language. The so called subordinate bilinguals or subsequent bilinguals usually learned their additional language (it can be the second, third etc. language!) in a formal environment like school. – Please read our post about the difference between language acquisition and language learning …
We can not see and sometimes not hear the difference between the kind of bilinguals. Thanks to recent studies in neuroscience and bilingualism we can tell more about how bilingualism affects the brain.
With regards to the CPH (Critical Period Hypothesis) it needs to be clarified that this hypothesis which became popular thanks to Eric Lenneberg’sBiological Foundations of Language in 1967, and later picked up by Noam Chomsky, has mislead some scholars. This hypothesis states that there are “maturational constraints on the time a first language can be acquired”, and “after this period language cannot be acquired in a natural fashion”, fact is that the study focused on abused, i.e. neglected children who had been deprived of first language in early childhood. And this hypothesis is valid for L1, the first language or languages, not the second or additional ones.
Although it is not clear if the deprivation of language input and stimulation in these children is the only reason for their language acquisition difficulties (Sampson 1997, 37), “it is not certain if children in cases of extreme deprivation have trouble learning language because they have missed their so-called “critical period” or if it is because of the extreme trauma they have experienced.” – This means that a person that is exposed to regular language input and stimulated to communicate in it will be able to acquire and learn a language no matter the age!
The main difference between adults and children acquiring/learning languages is that adults tend to have a more rational approach to learning additional languages in adulthood because the conventional way these are taught is more analytical, focusing on the structure of the language (grammar, rules, differences in phonology, morphology, syntax, vocabulary, prosody etc.), and does not focus on repeating words and sentences the way young children acquire languages! – Please read also this post about “The Earlier the Better?” or watch my video about it:
The approach is different and “more natural”. Of course, adults will try to connect all the new data with data they already know, i.e. the language structure of the other languages they already know, but an approach that doesn’t focus primarily on grammar and rules is proving not only more time efficient – because more engaging – but also more effective concerning the emotional understanding of the new language.
What concerns the visible increase of brain density in bilinguals and multilinguals is a fact and one of the most quoted advantages of speaking multiple languages. The “involvement of the dorsolateral prefrontal cortex which plays a role in executive function, problem solving, switching between tasks and focussing while filtering out irrelevant information”, makes the brain of multilinguals more healthy and actively engaged. No matter when one learns another language: it’s never too late!
On a side note: What is said about Alzheimer and Dementia in the aforementioned video is not only related to bilingualism. The same beneficial effect can be observed in people who engage their brain actively on a regular basis.
* in linguistics we also use terms like simultaneous, additive, consecutive (or sequential), balanced, receptive, early, late and subtractive bilinguals, depending on the aspect we are focusing on.
If you want to know how our brain changes if we speak two or more languages, I recommend you to watch (listen to) this video too:
About multilingualism or polyglots and their brain functioning, please watch Xaver Funk’s presentation Polyglot Science at the Polyglot Conference 2020