爱华网耶尔德赫吉特·巴塔查尔吉/撰文
比起只会说一种语言的人，双语者在这个日益全球化的世界中显然更有用。但近些年，有科学家提出，说两种语言的人比那些广交朋友的人来说，有更为本质的优势。事实证明，说双语能使你更聪明。且对你的智力有更为深远的影响，改善语言之外的认知能力，甚至防治老年痴呆。
这种“双语”观点与20世纪多数人对通晓两种语言的理解有相当大的差异。就认知来说，研究人员、教育工作者和决策者长久以来认为第二语言是一种干扰， 那会阻碍儿童的在学业和思维上的发展。
没错，干扰是存在的：足够的证据表明，即便是在只用一种语言的时候，有两种语言系统的大脑也会发生干扰，如此，设置某种情境便会阻碍另一种语言系统的发挥。但是研究者发现这种干扰不仅不是阻碍反而因祸得福。它迫使大脑解决内部的冲突，给思维以提大脑认知力的锻炼。
举例来说，懂双语的人比那些只懂一种的好像更擅长解决某些智力上的难题。心理医生艾伦·比亚维斯托克和米歇尔·马丁李，2004年进行了一项实验。分别要求两组学龄前儿童，会双语的和只懂一种语言的，选出显示在电脑上蓝色的圆形和红色方块。然后放进标有蓝色的方块和红色的圆形的虚拟盒子中。
第一项，孩子们依据颜色来挑选形状，把蓝色的圆放进有蓝色方块标识的盒中，把红色方块放进有红色圆形标识的盒中。两组都完成得相对轻松。第二项，让孩子们依形状来选择，这个任务更具挑战性是因为这需要把相应的图形放置在有颜色冲突的盒子里。这一番，懂双语的孩子完成得更快。
一系列实验得出的大量的证据表明，具备双语的经验改善了大脑的所谓“执行功能”，也就是我们用于想办法、解决问题、完成不同脑力工作，引导注意力过程的指挥系统。这种过程包括集中精神防止溜号，有意识地转移关注点，牢记信息——像在开车的同时要记住一连串方向的顺序。
为什么这两种并行语言系统的角力会改善认知方面的能力？直到最近，研究人员发现双语者的优势根源于锻炼出的抑制力，在实践中磨练出抑制某一种语言系统的能力：这种抑制力被认为，有助于培养双语思维避免在不同情境下走神。但这种解释似乎并不充分，因为有研究表明双语者即便在完成不需要抑制力的任务时，也比单语者表现得更好，比如用线把任意散乱在纸上的一堆数字按由小到大的顺序穿起来。
双语者和单语者差异的关键可能更为根本：对外界有更敏感的监控力。“双语者不得不相当频繁地转换语言——可能对父亲讲某种语言同时对母亲讲另一种”，一个来自西班牙庞培法布拉大学的研究人员，阿尔伯特·科斯塔如是说。“需要保持跟上周遭变化，这与在开车的同时对周围环境的把握是一致的。”在一项对比会德语和意大利语的双语者和只会意大利语的人的监控测试中，科斯塔和他的同事发现双语者不仅表现得更好，而且大脑用到监控周围的部分也更少，也就是说他们在监控上更为有效率。
双语的经历似乎从婴儿到老年时期一直对大脑产生影响。（有理由相信同样适用于那些后天习得第二语言的人）。
2009年意大利的里雅斯特，在这的国际学校进修的艾格尼丝·科瓦奇发现，将出生到七个月大就浸染在双语环境中的婴儿和在单一语言环境中成长的婴儿进行比较实验。实验之初，先让婴儿们听一段声音提示，然后在一旁的屏幕上显示出玩偶。两组婴儿都学会了看一旁的屏幕期待玩偶。但接下来的一组实验中，当玩偶出现在对面的屏幕上，其他婴儿尚无反应的时候，双语环境中成长的婴儿就迅速的明白转到新的方向上凝视玩偶。
双语效应也一直持续到人的晚年。圣地亚哥加州大学，神经心理学家塔尔玛·戈兰，在对44个讲“西班牙语-英语”的老年人的研究中发现，双语能力高的个人———衡量通过评估使用每种语言的相对熟练程度——相比其他人更能抵御痴呆的发作和阿尔茨海默症（老年痴呆）：双语水平越高，发生年龄越迟。
没人怀疑过语言的力量。但是谁能想到我们听见的词和我们说过的话能留下如此深刻的烙印？
耶尔德赫吉特·巴塔查尔吉是本报科学版特约撰稿人。
【纽约时报】说双语者为什么更聪明？
Why Bilinguals Are Smarter
By YUDHIJIT BHATTACHARJEE
SPEAKING two languages rather than just one has obvious practical benefits in an increasingly globalized world. But in recent years, scientists have begun to show that the advantages of bilingualism are even more fundamental than being able to converse with a wider range of people. Being bilingual, it turns out, makes you smarter. It can have a profound effect on your brain, improving cognitive skills not related to language and even shielding against dementia in old age.
This view of bilingualism is remarkably different from the understanding of bilingualism through much of the 20th century. Researchers, educators and policy makers long considered a second language to be an interference, cognitively speaking, that hindered a child’s academic and intellectual development.
They were not wrong about the interference: there is ample evidence that in a bilingual’s brain both language systems are active even when he is using only one language, thus creating situations in which one system obstructs the other. But this interference, researchers are finding out, isn’t so much a handicap as a blessing in disguise. It forces the brain to resolve internal conflict, giving the mind a workout that strengthens its cognitive muscles.
Bilinguals, for instance, seem to be more adept than monolinguals at solving certain kinds of mental puzzles. In a 2004 study by the psychologists Ellen Bialystok and Michelle Martin-Rhee, bilingual and monolingual preschoolers were asked to sort blue circles and red squares presented on a computer screen into two digital bins — one marked with a blue square and the other marked with a red circle.
In the first task, the children had to sort the shapes by color, placing blue circles in the bin marked with the blue square and red squares in the bin marked with the red circle. Both groups did this with comparable ease. Next, the children were asked to sort by shape, which was more challenging because it required placing the images in a bin marked with a conflicting color. The bilinguals were quicker at performing this task.
The collective evidence from a number of such studies suggests that the bilingual experience improves the brain’s so-called executive function — a command system that directs the attention processes that we use for planning, solving problems and performing various other mentally demanding tasks. These processes include ignoring distractions to stay focused, switching attention willfully from one thing to another and holding information in mind — like remembering a sequence of directions while driving.
Why does the tussle between two simultaneously active language systems improve these aspects of cognition? Until recently, researchers thought the bilingual advantage stemmed primarily from an ability for inhibition that was honed by the exercise of suppressing one language system: this suppression, it was thought, would help train the bilingual mind to ignore distractions in other contexts. But that explanation increasingly appears to be inadequate, since studies have shown that bilinguals perform better than monolinguals even at tasks that do not require inhibition, like threading a line through an ascending series of numbers scattered randomly on a page.
The key difference between bilinguals and monolinguals may be more basic: a heightened ability to monitor the environment. “Bilinguals have to switch languages quite often — you may talk to your father in one language and to your mother in another language,” says Albert Costa, a researcher at the University of Pompea Fabra in Spain. “It requires keeping track of changes around you in the same way that we monitor our surroundings when driving.” In a study comparing German-Italian bilinguals with Italian monolinguals on monitoring tasks, Mr. Costa and his colleagues found that the bilingual subjects not only performed better, but they also did so with less activity in parts of the brain involved in monitoring, indicating that they were more efficient at it.
The bilingual experience appears to influence the brain from infancy to old age (and there is reason to believe that it may also apply to those who learn a second language later in life).
In a 2009 study led by Agnes Kovacs of the International School for Advanced Studies in Trieste, Italy, 7-month-old babies exposed to two languages from birth were compared with peers raised with one language. In an initial set of trials, the infants were presented with an audio cue and then shown a puppet on one side of a screen. Both infant groups learned to look at that side of the screen in anticipation of the puppet. But in a later set of trials, when the puppet began appearing on the opposite side of the screen, the babies exposed to a bilingual environment quickly learned to switch their anticipatory gaze in the new direction while the other babies did not.
Bilingualism’s effects also extend into the twilight years. In a recent study of 44 elderly Spanish-English bilinguals, scientists led by the neuropsychologist Tamar Gollan of the University of California, San Diego, found that individuals with a higher degree of bilingualism — measured through a comparative evaluation of proficiency in each language — were more resistant than others to the onset of dementia and other symptoms of Alzheimer’s disease: the higher the degree of bilingualism, the later the age of onset.
Nobody ever doubted the power of language. But who would have imagined that the words we hear and the sentences we speak might be leaving such a deep imprint?
Yudhijit Bhattacharjee is a staff writer at Science.
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