We know that the language we speak shapes how we see the world, affecting everything from our sense of direction to how we see colors.
But the languages we know — even simply the language we first heard as infants — affect the way our brain works.
A 2009 study published in Current Biology found that the cries of French infants were noticeably different from those of German babies.
Researchers recorded the cries of 30 French newborns and 30 German ones and grouped them together to look for patterns. They discovered that German babies' cries start out more intense and get softer while French babies' cries were most intense at the end.
What would cause this?
An early ear for language
Babies are able to hear for about three months before they're born. Although they don't understand the words, they hear how language sounds, such as whether speech starts off softly or more intensely.
In short, even when they're still in the womb, their understanding of how language should sound are already being formed.
But what if we're exposed to a language early on and grow up learning a different one?
Scientists were interested in whether such an experience would leave a lasting effect on the brain, so Canadian researchers conducted a study with 48 adopted children who ranged in age from 9 to 17. The children's average age of adoption was 12.8 months.
Some of the study participants were born and raised in a French family and spoke only French. Some were Chinese-born and adopted into French families and spoke only French. Others were fluent in both French and Chinese.
All three groups listened to Chinese language sounds while MRI scans were taken of their brains.
Those who spoke Mandarin would know that depending on the tone of the sound, it could mean different things, while those who didn't speak the language would ascribe no meaning to the sounds.
They heard three syllable sounds and were then asked to press a button to indicate if the final syllable sounded the same or different.
All three groups could tell the sounds apart, but they used different parts of their brains to figure this out.
The group that had never learned Mandarin used the right half of the brain, the part that processes non-language sounds. However, both the groups that knew Mandarin and that head heard it as infants — but didn't speak it — used the languages areas in the left half of their brains.
In short, those who had heard Mandarin as infants were able to recognize that the sounds they heard were meaningful even though they didn't understand them.
"What is kind of striking is that these traces are there even though they don't really need them anymore," writes co-author Denise Klein of the Montreal Neurological Institute and Hospital at McGill University.
Previous research has shown that infants initially respond to all languages they hear, but as weeks pass, they stop turning their heads in response to languages that aren't their parents' spoken languages.
"Like everything in life, we have to prune out what is irrelevant and focus on what is relevant," Klein wrote.
So why would the brain continue to process a language we no longer speak as meaningful? Scientists aren't sure.
Research has also shown that, based on how brains operate, knowing more than one language gives people several advantages.
For example, bilingual children are better at ignoring classroom noise than those who speak only one language, and some studies have found that speaking multiple languages helps stave off dementia.
Recently, a study published in the journal Brain & Language found that bilingual people are more efficient at higher-level brain functions.
Researchers used functional magnetic resonance imaging to scan the brains of 17 people who were fluent in both Spanish and English and 18 who spoke only English.
Participants heard the name of an object and were simultaneously shown a picture of that object, as well of one with a similar name and two unrelated objects. They were instructed to quickly pick the object that showed the word they heard.
Bilingual people performed the task fastest even though their brains lit up in fewer regions involved in higher-level functions than that of their monolingual counterparts' brains.
In other words, the brains of those who spoke only English had to work harder to perform the same task.
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