Under the Hood

Your Mother Tongue Sticks With You Even If You Forget It, As Sounds Leave Lasting Impression

baby talking
What you learn as a baby sticks with you for a very long time. Photo courtesy of Shutterstock

You may have forgotten a language you once heard briefly during infancy, but your brain hasn’t. A new study has shown that language is able to leave a lasting impression on the brain, even if the individual has long forgotten the language or never completely learned it to begin with. This research supports past studies that suggested the importance of language input during the first year of a child’s life.

Once Heard, Never Forgotten

A total of 48 girls were involved in the study, aged 9 to 17, according to the press release. The girls were born and raised in different environments. Some of them were raised in French-speaking families and could only speak French. Others were born in China but were adopted and raised in French families from an early age and could therefore only speak French. The last group consisted of young girls who were fluent in both French and Chinese.

For the study, the researchers had all three groups of girls listen to Chinese language while magnetic resonance imaging (MRI) scans were taken of their brains. The sounds they listened to, depending on the intonation, could mean different words in the Chinese language. However, to the untrained ear, these sounds could be more difficult to differentiate. After hearing the sounds, the girls were then instructed to press a button to indicate whether the recordings sounded the same or different.

Results showed that all groups of girls were quite successful in telling about the Chinese sounds. However, the brain scan revealed that although the girls may have been able to tell the sounds apart, only some of the participants registered recognition of the sounds.

The MRI scans of the bilingual Chinese-French and the children adopted from China who had long forgotten the language they were exposed to in their early development showed something that the researchers described as “linguistic relevance.” Both their right and left hemispheres showed brain activity. The left temporal cortex was also the center of activity in the bilingual and Chinese adopted children.

“These regions have consistently been recruited in previous research on tonal processing and are thought to be important for the processing of tone in speakers of tonal languages,” the study read.

In the children who had never been exposed to any Chinese language, only the right hemisphere showed activity.

How Language Works

According to these results, the researchers concluded that exposure to Chinese as a baby, even if it was never properly learned and long forgotten, still enabled the children to understand that what they were hearing was a “language, or meaningfully related,” said co-author Denise Klein, of the Montreal Neurological Institute and Hospital at McGill University, the NY Daily News reported.

It’s believed that this finding is connected to the idea of there being “a special status for language input obtained during the first year of development,” the study read.

Most humans are able to master a language by the time they are 5 years of age. This phenomenon is observed throughout the world, regardless of the tongue a child is exposed to. Although science is not exactly clear on how children are able to complete this task, which takes most adults a lifetime to do, they have some ideas.

Research has shown that all babies are born with an almost rule book to human language. The famed linguist Noam Chomsky first introduced this concept with his idea of "universal language," a certain knowledge of syntax and grammar that all children are born with. This would allow children to differentiate language's other sounds. However, what was not previously known was how permanent this early language exposure actually was.

The next step for the team is to find out if early exposure to a long forgotten language makes it easier for individuals to relearn the language later in life. Findings from this study could stretch even further and shed light on how the unconscious influences of early childhood go on to affect later development.

Source: Pierce LJ, Klein D, Chen JK,  Delcenserie A, Genesee F. Mapping the unconscious maintenance of a lost first language. PNAS. 2014.

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