使用雙語 增強腦力防癡呆

作者： 楊明暐╱綜合報導 | 中時電子報 – 2012年5月4日 上午5:30

中國時報【楊明暐╱綜合報導】

美國西北大學的科學家相信，學習第二種語言能增強腦力。他們宣稱，使用雙語對大腦是一種訓練，等於進行一種讓心智更健康的智力「運動」。

西北大學科學家在美國《國家科學院學報》發表研究報告，提供「生物學」證據，證明說兩種語言對腦部有深遠影響，並改變神經系統對聲音的反應。

科學家找來四十八名健康的大學生，檢測他們腦部對不同聲音產生的反應，其中有廿三人使用雙語，研究人員用頭部電極記錄他們的腦波圖形變化。

結果發現，在實驗室安靜的環境下，說雙語者與只說英語者的腦波圖形類似。但在嘈雜環境下，說雙語者大腦處理聲音的能力，遠勝過只會一種語言的人。他們更能吸收重要資訊，比如演講者的聲音，並過濾掉背景閒聊聲等分散注意力的雜音。

領導這項研究的克勞斯說：「說雙語強化了聲音的經驗，培養出的聽覺系統對自動化聲音處理，特別是處理具有高度挑戰或異常聆聽環境下的聲音，具有更高效率、彈性且更專注。」
參與研究的馬瑞安指出，人們玩填字遊戲和其他活動來保持腦力，而實驗顯示，使用雙語的好處甚多，能夠提升注意力、抑制力以及對聲音的解碼能力。過去類似的研究還顯示，使用雙語有助於防止早老性癡呆。

下面是紐約時報全文報導的摘要：

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 Pompeu 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.