Learning a second language can improve brain power, scientists believe. US researchers from Northwestern University say bilingualism(双语) is a form of brain training — a mental "work out" that adjusts the mind finely.
Speaking two languages well affects the brain and changes how the nervous system reacts to sound, lab tests showed. Experts say the experiment performed by the National Academy of Sciences provides "biological" evidence of this.
In an attempt to prove the guess that speaking two languages is good for one's mind, the team monitored how the brain of 48 healthy student volunteers reacted to different sounds. Twenty three of these volunteers were bilingual.
The scientists used special equipment to trace the pattern of brainwaves. Under quiet, laboratory conditions, the bilingual students responded in a similar way to the English-only-speaking students, who formed the control group. But the bilingual group were far superior at processing sounds even when there were a lot of people talking in the room. They were better able to focus on to the important information — the speaker's voice — and block out other distracting noises.
Prof Nina Kraus, who led the research, said: "The bilingual's better experience with sound results in a hearing 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 double language speakers come automatically simply from knowing and using two languages.''
Musicians appear to gain a similar benefit when rehearsing(彩排), say the researchers. According to some theories, being bilingual might help avoid dementia（痴呆）.
What’s the purpose for the lab test led by Prof Nina Kraus?

A．To find how better the bilingual students can react to sound than other students.

B．Just to find scientific proof for a previous guess.

C．To show the students how good it is to learn a second language.

D．To find a way to prevent dementia.

What does the underlined word “distracting” mean?

A．tiring	B．exciting
C．interesting	D．disturbing

What does Viorica Marian seem to believe?

A．People should do crossword puzzles to keep their minds sharp.

B．Bilingual students have more advantages in study than non-bilingual ones.

C．Speaking two languages is an easier way for people to increase their brain power.

D．Bilingual students are better at solving crossword puzzles.

What conclusion could be drawn from the passage?

A．Being bilingual strengthens brain power.

B．Speaking a second language can change your nervous system.

C．Bilingual musicians perform better on stage.

D．The English-only-speaking students can concentrate easily.

How was the bilingual group better at processing sounds?

A．They were the control group.

B．They could better fix their attention on something of importance.

C．They were able to find the speaker’s voice quickly.

D．They had better nervous system.