Because all types of bilingual people can become fully proficient in a language regardless of accent or pronunciation,
上述三种双语使用者，他们至少都能精通一种语言，无论是在腔调或是发音方面，
the difference may not be apparent to a casual observer.
因此，一般人难以发觉这三种类型的差异。
But recent advances in brain imaging technology have given neurolinguists a glimpse into
然而现在，由于大脑成像技术不断进步，神经语言学家得以窥探
how specific aspects of language learning affect the bilingual brain.
语言学习对于双语使用者的大脑产生何种影响。
It's well known that the brain's left hemisphere is more dominant and analytical in logical processes,
大家都知道，大脑的左半部主要掌管逻辑思考与分析，而右半脑则掌管情感与社交活动，
while the right hemisphere is more active in emotional and social ones,
虽然左、右半脑有所区别，
though this is a matter of degree, not an absolute split.
但并非完全独立运作。
The fact that language involves both types of functions while lateralization develops gradually with age,
事实上，语言同时包括了左脑与右脑的功能，而随着年纪增长，大脑功能逐渐侧重其中一边，
has lead to the critical period hypothesis.
这个观点发展出关键时期的假说。
According to this theory, children learn languages more easily
根据这个理论，儿童通常学习语言较快，
because the plasticity of their developing brains lets them use both hemispheres in language acquisition,
是因为大脑仍在发展，因此仍具有可塑性，他们可以同时利用左、右两边的大脑学习语言；
while in most adults, language is lateralized to one hemisphere, usually the left.
然而，多数成人会偏向採用其中一侧的大脑来学习语言，通常是左半脑。
If this is true, learning a language in childhood may give you a more holistic grasp of its social and emotional contexts.
如果这个观点正确，那么从小就学习语言，能够更容易掌握语言的社会和情感脉络。
Conversely, recent research showed that people who learned a second language in adulthood
相反地，最新的硏究指出：
exhibit less emotional bias and a more rational approach
如果人们到了成年之后才学第二种语言，
when confronting problems in the second language than in their native one.
当他们遇到有关新语言的学习问题时，会呈现出较少的情绪偏见，也会有较为理性的思考。
But regardless of when you acquire additional languages, being multilingual gives your brain some remarkable advantages.
无论如何，当你学习新的语言时，可以替你的大脑带来明显的好处。
