LinguaLive Lv.2 20200901

The benefits of a bilingual brain

¿Hablas español? Parlez-vous français? 你会说中文吗？ 

If you answered, "sí," "oui," or "会" and you're watching this in English, chances are you belong（属する）to the world's bilingual and multilingual majority. 

And besides（〜の他にも）having an easier time travelling or watching movies without subtitles, knowing two or more languages means that your brain may actually look and work differently than those of your monolingual friends. So what does it really mean to know a language? 

Language ability is typically measured in two active（能動態）parts, speaking and writing, and two passive（受動態）parts, listening and reading. While a balanced bilingual has near equal abilities across the board in two languages, most bilinguals around the world know and use their languages in varying proportions. And depending on their situation and how they acquired each language, they can be classified（分類された）into three general types. 

For example, let's take Gabriella, whose family immigrates（移住する）to the US from Peru when she's two-years old. As a compound（混合する）bilingual, Gabriella develops two linguistic codes simultaneously（同時に）, with a single set of concepts, learning both English and Spanish as she begins to process the world around her. Her teenage brother, on the other hand, might be a coordinate bilingual, working with two sets of concepts, learning English in school, while continuing to speak Spanish at home and with friends. Finally, Gabriella's parents are likely to be subordinate bilinguals who learn a secondary language by filtering it through their primary language. 

Because all types of bilingual people can become fully proficient（熟練した）in a language regardless（〜にかかわらず）of accent or pronunciation, the difference may not be apparent to a casual observer. But recent advances in brain imaging technology have given neurolinguists（神経言語学者）a glimpse into how specific aspects of language learning affect the bilingual brain. 

It's well known that the brain's left hemisphere（半球）is more dominant and analytical in logical processes, while the right hemisphere is more active in emotional and social ones, though this is a matter of degree, not an absolute split. 

The fact that language involves both types of functions while lateralization（局在）develops gradually with age, has led to the critical period hypothesis（臨界期仮説）. According to this theory, children learn languages more easily because the plasticity（柔軟性）of their developing brains lets them use both hemispheres in language acquisition（習得）, while in most adults, language is lateralized to one hemisphere, usually the left. 

If this is true, learning a language in childhood may give you a more holistic（全体的な）grasp of its social and emotional contexts. Conversely（逆に言えば）, recent research showed that people who learned a second language in adulthood exhibit less emotional bias and a more rational（合理的）approach when confronting（直面する）problems in the second language than in their native one. But regardless of when you acquire additional languages, being multilingual gives your brain some remarkable advantages. 

Some of these are even visible, such as a higher density（密度）of the grey matter that contains most of your brain's neurons（神経細胞）and synapses（シナプス「神経細胞の接続部」）, and more activity in certain regions when engaging a second language. The heightened（高まった）workout a bilingual brain receives throughout its life can also help delay the onset of diseases, like Alzheimer's and dementia by as much as five years. The idea of major cognitive benefits to bilingualism may seem intuitive（直感的）now, but it would have surprised earlier experts. 

Before the 1960s, bilingualism was considered a handicap that slowed a child's development by forcing them to spend too much energy distinguishing between languages, a view based largely on flawed（欠点のある）studies. 

And while a more recent study did show that reaction times and errors increase for some bilingual students in cross-language tests, it also showed that the effort and attention needed to switch between languages triggered more activity in, and potentially strengthened, the dorsolateral prefrontal cortex（背外側前頭前野）. This is the part of the brain that plays a large role in executive function, problem-solving, switching between tasks, and focusing while filtering out irrelevant（無関係な）information. 

So, while bilingualism may not necessarily make you smarter, it does make your brain more healthy, complex and actively engaged, and even if you didn't have the good fortune of learning a second language as a child, it's never too late to do yourself a favour and make the linguistic leap from, "Hello," to, "Hola," "Bonjour" or "你好’s" because when it comes to our brains a little exercise can go a long way.