The language we are exposed to in infancy – and perhaps even in utero – have a profound impact on our linguistic capabilities, as exhibited in a 2014 study of Chinese adoptees in Canada. A 2014 study conducted by the University of Washington, ‘Mapping the unconscious maintenance of a lost first language’, showed that internationally adopted children from China, exposed exclusively to Canadian French they were, on average, 12.8 months, maintained neural representations of Mandarin despite not speaking a word of it.
Mandarin is a tonal language, with four tones: flat, rising, falling, and one that falls and then rises. They are difficult to distinguish for speakers of non-tonal languages, such as English or French. As shifts in tone signify shifts in meaning, this can prove problematic. 熊猫 and 胸毛 are both romanized as xiongmao, but the former means “panda” and the latter means “chest hair”.
The children in the study, who had no exposure to Chinese for an average of 12.6 years, recognized the prosody of Mandarin – its patterns of stress and intonation – in the same way as bilingual French-Chinese speakers, and in contrast to the control group of French speakers who had never been exposed to Chinese.
Neuroplasticity And Language Learning
Despite its enormous capacity for change, the brain is relatively fixed when it comes to language learning – for example, people who start learning a second language as adults almost always retain an accent, even when their grammar is at the level of a native speaker.
This suggests that the neural pathways associated with sentence structure are more malleable than those associated with phonetics. The brain is particularly sensitive to external stimuli in the first few years after birth. This is in line with the critical period hypothesis, according to which language acquisition is much easier before a certain cut-off age.
All babies are born with the ability to distinguish sound categories present in all the world’s languages, but within months of birth this ability is reduced to the languages they are exposed to – the brain filters out what is not useful for its development.
During the MRI scans performed during the study, the internationally adopted children, as well as the bilingual French-Chinese speakers, showed activity predominantly in the left hemisphere when listening to Chinese, while for children who were not exposed to Chinese in their first year of life, the right hemisphere was predominantly active – the former had developed neural pathways for processing their lost mother tongue. This held true regardless of their current age (participants ranged from 9 to 17) and how recently they had been exposed to Chinese. The language they heard long before they were old enough to understand it was inscribed in their brains.
Weeping, lullabies, and in-utero development
The University of Washington study suggests that language heard months after birth has a profound effect on how a person interacts with language as they grow up. The same could be said for speech heard even earlier – during foetal development.
A 1988 French study found that in late pregnancy a foetus can clearly hear the rising and falling intonation of speech. This was determined by placing microphones in the wombs of women about to give birth and asking them to recite nursery rhymes. Although the sounds were muffled, the prosody was clearly audible.
The fact that a child is born familiar with the melody and cadence of the language it is likely to grow up speaking is significant. Babies exercise their ability to produce sound as soon as they are born by crying loudly. Even as they perform this first gesture, they are already reflecting the languages they were exposed to in utero. A 2019 study by Kathleen Wermke found that new-born babies’ cries matched the tonality of their mother’s language. While babies born to French-speaking mothers cried with the rising cadence of French, those whose mothers spoke Mandarin – or the related nine-tone Cantonese – had more complex cries that reflected the prosody of their respective languages.
The studies mentioned in this article demonstrate the remarkable influence of early language exposure on neural representations and language capabilities.
The ability to recognize and distinguish tonal languages, such as Mandarin, even without active use, highlights the lasting impact of early exposure on neural pathways. The critical period hypothesis further emphasizes the importance of early language exposure, as the brain becomes less receptive to external stimuli as a person grows older. Even before birth, a child’s exposure to the prosody of their mother’s language can shape their cries and potentially impact their language development later on.
These findings underscore the value of early language exposure and suggest that language learning is a complex and deeply ingrained process in the human brain.