Acquired in our first years of life, the first language we learn is special. In many respects, the complexity of the human language is one of the important characteristics that distinguishes us from other animals. The complexity of the sounds we can make and our grammar-filled writing system are things that take the better parts of our lives to master. In the process of this mastery, our brain plays a crucial role that often goes unnoticed: a role that begins in our infancy.
In the last decade, a variety of research has come to show that our ability to absorb and learn language begins very early in life with the recognition of sound. Two pieces of research published in 2014 and 2015 from McGill University highlight this important relationship between sound and language, showing how the age of exposure to sound can affect the way our brains respond to language. This research made use of three groups of children, aged from 10 to 17, to see how language exposure before the age of three affects the brain’s response to linguistic sound. The first group of children consisted of monolingual French children who had only been exposed to French since birth and had no other experience with a second language. The second group consisted of bilingual children who had been exposed to both French and Chinese before the age of three and maintained use of both languages. The third group consisted of internationally adopted children from China, children adopted by French parents. These children were all adopted before the age of three, meaning they were exposed to Chinese first and then French second with the exposure to Chinese discontinuing upon adoption.
In the 2014 study, all three groups of children listened to various sounds while their brain activity was being observed with functional MRI. This is a technique that looks to see which areas of the brain activate when presented with a stimulus. In one of the tests, the sound children heard was a linguistic element present only in Chinese and not French. On hearing the sound, the brain activation of the adopted children and that of the bilingual children matched precisely but were very different from the activation of the monolingual children. This result indicates that exposure to our first language is so deeply ingrained that our response to it is not overwritten in the brain even when we stop using it and start using a second, entirely new language.
The 2015 study took this process a step further and presented the children with French pseudo-words. These are fake words that follow French pronunciation rules but don’t actually mean anything (words like vapagne, chansette). These words were used because they represent the sounds of French but do not contain any meaning or grammar, ensuring that the brain response is only because of the sound. As in the previous study, the brain activations were different between groups with different first languages. The monolingual group showed brain activation indicative of a traditional language response. This activation occurred primarily in the regions of the brain responsible for verbal communication. The two Chinese groups, on the other hand, showed brain activation that was not so specific for a traditional language response. Most strikingly, these children exhibited much stronger responses in areas of the brain not associated with verbal communication. The areas that were activated were associated instead with general attention and cognitive control, something not observed in the monolingual group. These results suggest the striking and surprising possibility that the human brain may actually use different regions to learn a first and second language.
When observed in the larger context of research on second language acquisition, this result is surprisingly consistent with other data that shows infants are much better at acquiring new language through sound and listening than adults. The research from McGill would therefore offer a very powerful and consistent explanation for why adult second language learning is more efficient through reading and writing as both skills can be amplified and made more efficient through high levels of general attention and cognitive control.
Huang Xu is an undergraduate student in the School of Life Sciences at Fudan University.
Justin Fendos is a Ph.D. from Yale and a professor at Dongseo University in Busan. He is also the associate director of the Tan School of Genetics at Fudan University, Shanghai, and a National Academy of Sciences Teaching Fellow.
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