¿Hablas español? Parlez-vous français? ni hui shuo zhong wen ma? If you answered “si”,”oui” or ”hui” and you are watching this in English, chances are you belong to the world bilingual and multilingual majority. And besides having an easier time traveling, 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?

你会说中文吗？如果你能回答“si”、“oui”或者“是的”，而且能看懂这个英文短片，那么你就跟世界上很多人一样、具备双语能力或是多语能力。除了旅游时沟通比较方便、看电影不需要字幕这些好处之外，通晓两种或者三种以上的语言，意味着你的大脑在结构上或运作上与你那些单一语言的朋友有着明显的不同。所以到底什么才能算通晓一门语言呢？

Language ability is typically measured in two active parts, speaking and writing, and two passive 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 vary proportions. And depending on their situation and how they acquired each language, they can be classified into three general types.

衡量语言能力，主要包含两个主动部分——说和写，和两个被动部分——听和读。虽然一个出色的双语者对于两种语言都有着相近的使用能力，但是大多数的双语者对两个语种的认知和使用能力是有差异的。根据个人所处的环境以及他们具体学语言的方法，双语者通常可以分成三类。

For example, let’s take Gabriella, whose family immigrates to the US from Peru when she was two-years old. As a compound bilingual, Gabriella develops two linguistic codes simultaneously, 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.

举个例子来说，Gabriella在两岁时跟着家人由秘鲁移民到美国。她属于复合型双语者，Gabriella在刚接触这个世界时就同时学英语和西班牙语，所以给她一个概念、她的大脑就能同时唤起两种语言信号。她有一个十几岁的哥哥，则属于协调型双语使用者，他运用两种不同的概念，一方面在学校学习英语，另一方面用西班牙语和家人、朋友交流。

Finally, Gabriella’s parents are likely to be subordinate bilinguals who learned a secondary language by filtering it through their primary language.

最后，Gabriella的父母，则属于从属型双语者。当他们学习外语（英语）时，需要通过母语进行翻译再进行学习。

Because all types of bilingual people can become fully proficient in a language regardless of accent and pronunciation, the difference may not be apparent to be a casual observer. But recent advances in imaging technology have given neurolinguists a glimpse into how specific aspects of language learning affect the bilingual brain.

如果不考虑口音和发音问题，这三种类型的双语者至少都算能精通一门语言。因此，一般人很难发现这三种类型的差异。然而现在，由于大脑成像技术不断进步，神经语言学家能够知道语言学习对双语使用者的大脑产生什么样的影响。

It’s well known that the brain’s left hemisphere 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.

大家都知道，大脑的左半球是掌管数据和逻辑分析的，而大脑的右半球则掌管情感与社交，但这并不是绝对的、只是比例多少的问题。

The fact that language involves both types of functions while lateralization develops gradually with age, has lead to the critical period hypothesis. According to this theory, children learn languages more easily because the plasticity of their developing brains let them use both hemispheres in language acquisition, while in most adults, language is lateralized to one hemisphere, usually the left.

语言同时包括了左脑和右脑的功能，而随着年龄的增长，大脑的功能会逐渐侧重其中的一边，语言学习的关键时期假说就是由这个事实引申出来的。根据这个理论，儿童学习语言更容易，是因为他们的大脑仍在发展、可塑性更强，他们可以同时调用左右两边大脑的机能来学习语言；然而多数成年人只通过大脑的一边（通常是左脑）学习语言。

If this is true, learning a language in childhood may give you a more holistic grasp of its social and emotional contexts. Conversely, recent research showed that people who learned a second language in adulthood exhibit less emotional bias and a more rational approach when confronting problems in the second language than their native one.

如果这个假说是真的，那么在儿童时期学习语言可以让你对其社会和情感内涵有着更整体的把握。另一方面，近期的研究表明，成年人学习外语时的情绪性偏见没那么多，同时相比于母语环境，他们在外语环境中遇到问题时也更为理性。

But regardless of when you acquire additional languages, being multilingual gives your brain some remarkable advantages. Some of these are even visible, such higher density of the gray matter that contains most of your brain’s neurons and synapses, and more activity in certain regions when engaging a second language. The heightened workout a bilingual brain receives throughout its life can also help delay the onset of diseases, like Alzheimers and Dementia by as much as 5 years.

无论如何，当你学习一门新的语言时，多语能力都会给你的大脑带来明显的好处。有些好处甚至是可视化的，比如大脑灰白质的密度增加，那里包含了大多数的神经元和突触，而且在学习外语时，大脑的部分区域会变得更加活跃。双语者的大脑可以持续不断地接收强化训练，这能让一些病症（如阿兹海默痴呆症和失智症）的发作推迟至5年以后。

The idea of major cognitive benefits to bilingualism may seem intuitive now, but it would have surprised earlier experts. Before the 1960s, bilingualism was considered a handicap that slowed the child’s development by forcing them to spend them too much energy distinguishing between languages, a view based largely on flawed studies.

双语能力对认知能力的有所帮助在现代来看是很好理解的，但是过去的专家一定会对这个观点大吃一惊。在1960年之前，人们认为使用双语对于儿童的成长来说是一种障碍，因为这需要儿童花费精力去分辨别不同语言，这种观点的产生源自有瑕疵的研究方法。

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. This is the part of brain that plays a large role in executive function, problem solving, switching between tasks, and focusing while filtering out irrelevant information.

最新的研究的确显示，在跨语言测验当中，使用双语的学生的反应时间与错误次数增加了；同时也表明，学生需要花费更多的努力和注意力进行语言的转换，这也使得前额叶脑区更加活跃、进而强化其机能。前额叶脑区主要影响执行、解决问题、多任务转换、集中注意力、排除无关信息的能力。

So, while bilingual 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 like a child, it’s never too late to do yourself a favor and make the linguistic leap from, ”Hello,” to “Hola”, ”Bonjour” or “ninhao’s” because when it comes to our brains a little exercise can go a long way.

虽然学习双语不一定能让你更聪明，但是它可以让你的大脑更加健康、多元和活跃。即使你在年幼时没有机会学习第二语言，但是现在学习永远不会太晚。从现在开始学一门外语吧，把“hello”转换成“Hola”、“Bonjour”、“你好”(本文作者母语为英语)等外语问候，即使只是小小的训练，也能对大脑有所帮助。