Thirteen-year-old Alex Denk of Maplewood, N.J., does a lot of his homework while keeping up to date3 on TV sports news. And while talking to friends, he listens to music on his MP3 player with an earbud4 in one ear. His friends don't mind. They usually have an earbud in one ear too.
Alex's neighbor, 16-year-old Adam Heller, claims that he listens to his iPod5 in half of his classes. Homework rarely gets Adam's full attention either. “I never just do homework, I'm either listening to music or text messaging6 people at the same time,” he says.
Welcome to the world of multitasking7! Instead of focusing on one task, today's teens often split their attention between two or more tasks at the same time. Psychologists say it often has costs that few people recognize. When serious thought is required, people learn less, waste more time, and make more mistakes if they multitask.
Brain Bottleneck8
Multitasking, say experts, is efficient only when at least one of the tasks can be managed by your brain without making mistakes, such as walking and talking at the same time. What your brain can't do as well is consciously process two complex streams of information at the same time.
Any complex mental9 task involves10 many areas of the brain. Even when two tasks are very different and don't involve the same areas of the brain, they still use many of the same nerves connecting the areas. Only so much data can pass through those nerves. “Multitasking makes it extremely hard to solve such things as a difficult math or chemistry problem,” says Marcel Just, a psychologist at Carnegie Mellon University.
Most people think multitasking occurs at the same time but the brain isn't capable of doing this if two or more things require conscious11 thought at the same time, instead, it switches12 back and forth between them. That is what happens when teens IM their friends while trying to do their homework, according to David Meyer, a psychologist at the University of Michigan. “Either it takes longer to get the tasks done, or the quality of the output decreases dramatically,” Meyer says. In psychology circles, that exchange is called the speed-accuracy tradeoff13—the tradeoff between how quickly a task can be done and the number of mistakes made while doing it.
Multitasking Madness
Sometimes the loss of speed or accuracy isn't a problem. People don't need to be optimally14 efficient all the time. But occasions arise when multitasking is particularly foolish—while driving, for example. Chatting on a cell phone can draw the driver's attention away from the road at just the wrong moment. Some research shows that cell phone15 use on the road impairs16 a driver's performance as much as drunk driving17 does.
Multitasking can also be rude when one of the tasks is communicating with others. “What you are saying to the other person is, ‘I don't think what you are saying is important,’” says Meyer. “‘I have other stuff I want to do.’”
Finally, multitasking causes a decrease in learning. “One of the problems multitasking creates is a lack of understanding instead of gaining an in-depth18 knowledge of what you are studying. You only skim19 the surface.” says Jordan Grafman, a cognitive20 neuroscientist at the National Institute of Neurological21 Disorders and Stroke22 in Bethesda, Md.
Alex seems to understand when multitasking isn't a good idea. He knows he can't write or do difficult homework in front of the television. And he won't wear an earbud when he's talking to an adult. Adam also knows if he focused on his homework he could get more done but he doesn't care if it takes longer.
(English Version From Junior Scholastic)
13岁的亚历克斯·邓科家住新泽西州梅普尔伍德市，他常常在做家庭作业的同时收看最新的电视体育新闻。与朋友们谈话的时候，他一边听着MP3播放器里的音乐，一只耳朵里插着耳塞。他的朋友们并不介意，他们的一只耳朵通常也戴着耳塞。
亚历克斯的邻居、16岁的亚当·海勒声称在一半的课堂上都要听他的iPod。家庭作业也很少能抓住他的全部注意力。“我从不单做作业，要么一边听音乐，要么同时给人发短信。”他说。
欢迎来到多任务处理的世界！如今的十几岁少年不再专注于一项任务，而是把他们的注意力同时分配给两项或更多的任务。心理学家们说这样做往往会付出代价，但很少有人能意识到。在必须认真思考的时候，如果人们同时处理多个任务，则获取的信息更少，浪费的时间更多，犯的错误也更多。
大脑瓶颈
专家们说，多任务处理仅在一种情况下有效，即当你的大脑能够正确无误地处理至少其中的一项任务，比如边走路边谈话。你的大脑所不能胜任的是在同一时刻有意识地处理两个复杂的信息流。
任何复杂的智力活动都涉及到大脑的很多区域。即使两项任务迥然有别，涉及的大脑区域也不相同，但它们仍然共用许多连接两个区域的神经。这些神经所能运载的信息是有限的。“在同时处理多个任务的情况下，要解答数学或化学之类的难题是极端困难的。”卡耐基梅隆大学的心理学家马赛尔·贾斯特说。
大多数人认为多任务处理是同时进行的，但如果两件或更多的事情要求同时有意识的思考的时候，大脑就不能胜任了；相反，它在这些事情之间来回切换。密西根大学心理学家大卫·麦耶说，这就是当十几岁的孩子一边试图做家庭作业，一边与朋友即时聊天所发生的情况。“要么完成这些任务所花的时间更长，要么完成任务的质量显著下降，”麦耶说。在心理学界，这种交换被称为"速度与准确性折衷"——即多快能完成一项任务与在此过程中所犯错误数量之间的折衷。
不理智的多任务处理
有时牺牲速度或准确性并不是什么问题，人们无需在所有时候保持最高的效率。但是多任务处理也有特不明智的时候——比如边开车边做别的事。用手机聊天可能恰恰在错误的时刻把驾驶员的注意力从道路上引开。一些研究表明，行车时使用手机对驾驶员操作造成的负面影响与醉酒驾车的程度相当。
当多任务处理中的其中一个是与别人交谈的时候，它还可能使你显得粗鲁。“你给另一个人传达的信息是，‘我认为你说的话不重要，’”麦耶说，“‘我有别的事情要做。’”
最后，多任务处理导致学习质量的下降。“多任务处理带来的问题之一是对所学内容缺乏理解，不能获得透彻的知识。你只是浮光掠影。”位于马里兰州贝塞斯达市的美国神经失常与中风研究院的认知神经学家乔丹·格拉福曼说。
亚历克斯似乎明白了何时采用多任务处理是不明智的。他知道不能在电视机前写作或做难度大的家庭作业，他也不会再戴着耳塞跟大人谈话。亚当也明白，假如他专心做作业的话，他可以更有效率，但他对延长时间并不在意。
1. overload n. 超载
2. IM=instant messaging 即时聊天
3. up to date 最新的
4. earbud n. 耳塞
5. iPod 苹果公司生产的音乐播放器
6. text message 发文字短信
7. multitasking 多任务处理
8. bottleneck n. 瓶颈
9. mental adj. 脑力的，智力的
10. involve v. 包含，涉及
11. conscious adj. 有意识的
12. switch v. 转换
13. tradeoff n. 交易，折衷
14. optimally adv. 最佳地，最优地
15. cell phone 手机
16. impair v. 损害，削弱
17. drunk driving 醉酒驾车
18. in-depth 深入的，彻底的
19. skim v. 浏览，略读
20. cognitive adj. 认知的
21. neurological adj.神经学上的
22. stroke n. 中风