BBC今天引用美国西北大学的研究人员的话说，操双语对大脑是一种训练，相当于“健脑体操”，让大脑更健康。研究人员对参加试验的48名身体健康的大学生的大脑对不同声音的反应进行检测。其中，23人能操双语。

科学家利用电极记录接受实验者的脑波图形变化，发现实验室里安静的环境下，能说双语者与只能说英语者的脑波反应图形是相似的。但是，在嘈杂的环境中，操双语者的大脑对声音的处理能力显然更优越。他们能更好的集中在重要的信息上，比如主讲者的声音，而挡住其它分散精力的声音，比如闲聊的背景声。

实验报告作者之一Viorica Marian博士说，人们用玩填字游戏和其它活动来保持脑力，但其实学习并使用双语所带来的效果更显著，包括注意力、抑制力和对声音的解码能力。此前进行的类似调查还显示，使用双语有助于防止早老性痴呆。

这样的话，英、美等英语国家的人因为母语就是国际通用语言，大多数人不需要学习一门外语，就少了做“健脑体操”的机会，很容易收到环境的干扰，可能会显得比较“笨”一些。去年一个旅游网站Hotels.com的调查显示，2/3的英国人一个外语单词也不会说，20%的受访者居然不懂近邻法国人的口头禅Bonjour(你好)。特别英国年轻人最“不思进取”，47%的16至24岁的人表示，他们从未在生活中说过学校里学过的外语。

Being bilingual 'boosts brain power'

Learning a second language can boost brain power, scientists believe.

The US researchers from Northwestern University say bilingualism is a form of brain training - a mental "work out" that fine-tunes the mind.

Speaking two languages profoundly affects the brain and changes how the nervous system responds to sound, lab tests revealed.

Experts say the work in Proceedings of the National Academy of Sciences provides "biological" evidence of this.

For the study, the team monitored the brain responses of 48 healthy student volunteers - which included 23 who were bilingual - to different sounds.

They used scalp electrodes to trace the pattern of brainwaves.

Under quiet, laboratory conditions, both groups - the bilingual and the English-only-speaking students - responded similarly.

But against a backdrop of noisy chatter, the bilingual group were far superior at processing sounds.

They were better able to tune in to the important information - the speaker's voice - and block out other distracting noises - the background chatter.

'Powerful' benefits
 
And these differences were visible in the brain. The bilingualists' brainstem responses were heightened.

Prof Nina Kraus, who led the research, said: "The bilingual's enhanced experience with sound results in an auditory system that is highly efficient, flexible and focused in its automatic sound processing, especially in challenging or novel listening conditions."

Co-author Viorica Marian said: "People do crossword puzzles and other activities to keep their minds sharp. But the advantages we've discovered in dual language speakers come automatically simply from knowing and using two languages.

"It seems that the benefits of bilingualism are particularly powerful and broad, and include attention, inhibition and encoding of sound."

Musicians appear to gain a similar benefit when rehearsing, say the researchers. Past research has also suggested that being bilingual might help ward off dementia.