研究：双语人士大脑反应速度更快

美国肯塔基大学的研究人员发现，能讲两种语言可以抑制大脑衰老的速度，双语人士的大脑反应速度也比只会讲一种语言的人要更快一些。不过，研究人员指出，该研究发现只适用于那些从10岁起就开始使用第二语言的双语人士。阿拉巴马大学医学院的一位神经生物学家称双语现象是一个“美妙的自然试验”，人们在成长过程中不断切换使用两种语言能够使认知反应速度和能力得到提升。研究人员指出，儿童学习第二语言并不会阻碍母语能力的学习和发展，反而会有促进作用。

Speaking two languages can actually help offset some effects of aging on the brain, a new study has found.

Researchers tested how long it took participants to switch from one cognitive task to another, something that's known to take longer for older adults, said lead researcher, Brian Gold, a neuroscientist at the University of Kentucky.

"It has big implications these days because our population is aging more and more," Gold said. "Seniors are living longer, and that's a good thing, but it's only a good thing to the extent that their brains are healthy."

Gold's team compared task-switching speeds for younger and older adults, knowing they would find slower speeds in the older population because of previous studies. However, they found that older adults who spoke two languages were able to switch mental gears faster than those who didn't.

But don't go out and buy Rosetta Stone just yet. The study only looked at life-long bilinguals, defined in the study as people who had spoken a second language daily since they were at least 10 years old.

First, Gold and his team asked 30 people, who were either bilingual or monolingual, to look at a series of colored shapes and respond with the name of each shape by pushing a button. Then, they presented the participants with a similar series of colored shapes and asked them to respond with what colors the shapes were by pushing a button. Finally, researchers presented participants with a series of colored shapes, but they mixed prompts for either a shape or a color to test participants' task-switching times.

The bilingual people were able to respond faster to the shifting prompts.

Researchers then gathered 80 more people for a second experiment: 20 young bilinguals, 20 young monolinguals, 20 old bilinguals, and 20 old monolinguals. This time, researchers used MRI scans to monitor brain activity during the same shape- and color-identifying tasks. Gold and his team found that bilingual people were not only able to switch tasks faster - they had different brain activity than their monolingual peers.

"It allows a sort of window into how the brains of people who have different cognitive processing abilities and are processing the same stimuli in different ways," said Kristina Visscher, a neurobiologist at the University of Alabama School of Medicine who did not work on the study.

Visscher called bilingualism a "beautiful natural experiment," because people grow up speaking two languages, and studies have shown that they reap certain cognitive benefits from switching between languages and determining which to respond with based on what's going on around them. The University of Kentucky researchers took it a step further by using brain imaging, which she said was "exciting."

Gold said he grew up in Montreal, where he spoke French at school and English at home, prompting relatives to question whether his French language immersion would somehow hinder his ability to learn English.

"Until very recently, learning a second language in childhood was thought of as dangerous," he said. "Actually, it's beneficial."