Be brainy, be bilingual 双语能增强大脑能力 Learning a second language can boost brain power, scientists believe. US researchers from Northwestern University say bilingualism is a form of brain training - a mental "work out" 锻炼 that fine-tunes 微调 the mind. Speaking two languages affects the brain and changes how the nervous system 神经系统 reacts to sound, lab tests 试验室测验 revealed. Experts say the work, put forward for peer-review 同级评估 in Proceedings of the National Academy of Sciences, provides "biological" evidence of this. In an attempt to prove the hypothesis 假想 that speaking two languages is good for one's mind, the team monitored 监视(什么) how the brains of 48 healthy student volunteers reacted to different sounds. Twenty-three of these volunteers were bilingual. The scientists used scalp electrodes 电极 to trace the pattern of brainwaves. Under quiet, laboratory conditions (在)试验室条件(下) , the bilingual students responded in a similar way to the English-only-speaking students, who formed the control group 控制组 . But the bilingual group was far superior at processing sounds even when there were a lot of people talking in the room. They were better able to tune in to 收听(什么东西) / 入耳 the important information - the speaker's voice - and block out 排斥(什么) other distracting noises. Prof Nina Kraus, who led the research, said: "The bilingual's enhanced experience with sound results in an auditory system 听觉系统 that is highly efficient, flexible and focused in its automatic sound processing 处理(什么) , especially in challenging or novel listening conditions." Co-author Vitoria Marian said: "People do crossword puzzles and other activities to keep their minds sharp 让(他们的)大脑敏捷 . But the advantages we've discovered in dual language speakers come automatically, simply from knowing and using two languages.'' Musicians appear to gain a similar benefit when rehearsing, say the researchers. According to some theories 理论 , being bilingual might help ward off 挡避(什么) dementia.