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But the ability to multiprocess has its limits, even among young adults. When people try to perform two or more related tasks either at the same time or alternating rapidly between them, errors go way up, and it takes far longer--often double the time or more--to get the jobs done than if they were done sequentially, says David E. Meyer, director of the Brain, Cognition and Action Laboratory at the University of Michigan: "The toll in terms of slowdown is extremely large--amazingly so." Meyer frequently tests Gen M students in his lab, and he sees no exception for them, despite their "mystique" as master multitaskers. "The bottom line is that you can't simultaneously be thinking about your tax return and reading an essay, just as you can't talk to yourself about two things at once," he says. "If a teenager is trying to have a conversation on an e-mail chat line while doing algebra, she'll suffer a decrease in efficiency, compared to if she just thought about algebra until she was done. People may think otherwise, but it's a myth. With such complicated tasks [you] will never, ever be able to overcome the inherent limitations in the brain for processing information during multitasking. It just can't be, any more than the best of all humans will ever be able to run a one-minute mile."
Other research shows the relationship between stimulation and performance forms a bell curve: a little stimulation--whether it's coffee or a blaring soundtrack--can boost performance, but too much is stressful and causes a fall-off. In addition, the brain needs rest and recovery time to consolidate thoughts and memories. Teenagers who fill every quiet moment with a phone call or some kind of e-stimulation may not be getting that needed reprieve. Habitual multitasking may condition their brain to an overexcited state, making it difficult to focus even when they want to. "People lose the skill and the will to maintain concentration, and they get mental antsyness," says Meyer.
IS THIS ANY WAY TO LEARN?
LONGTIME PROFESSORS AT UNIVERSITIES around the U.S. have noticed that Gen M kids arrive on campus with a different set of cognitive skills and habits than past generations. In lecture halls with wireless Internet access--now more than 40% of college classrooms, according to the Campus Computing Project--the compulsion to multitask can get out of hand. "People are going to lectures by some of the greatest minds, and they are doing their mail," says Sherry Turkle, professor of the social studies of science and technology at M.I.T. In her class, says Turkle, "I tell them this is not a place for e-mail, it's not a place to do online searches and not a place to set up IRC [Internet relay chat] channels in which to comment on the class. It's not going to help if there are parallel discussions about how boring it is. You've got to get people to participate in the world as it is."
Such concerns have, in fact, led a number of schools, including the M.B.A. programs at UCLA and the University of Virginia, to look into blocking Internet access during lectures. "I tell my students not to treat me like TV," says University of Wisconsin professor Aaron Brower, who has been teaching social work for 20 years. "They have to think of me like a real person talking. I want to have them thinking about things we're talking about."