Why Multitasking May Be Bad for Your Brain

Many researchers believe the human brain can't really perform two or more tasks simultaneously, as the word multitask implies.


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Are you reading this while thumbing through text messages, streaming a TV show online, or scribbling a note to your child's teacher? (Or maybe doing all three?) Don't congratulate yourself.

Even though most people think an amped-up, gadget-dependent lifestyle makes them more nimble, focused, and efficient, that may not be the case. In fact, many researchers believe the human brain can't really perform two or more tasks simultaneously, as the word multitask implies.

Rather, they say, the mind toggles between tasks. And while mindless activities like walking and chewing gum aren't a problem, the brain doesn't fare well when people double up on complex tasks, such as driving and talking on a cell phone.

"Something's got to give," says David E. Meyer, PhD, director of the Brain, Cognition, and Action Laboratory at the University of Michigan, in Ann Arbor. "Either your cell phone conversation will suffer or your driving will suffer."

And it's not just behind the wheel. There's mounting evidence that multitasking can slow you down no matter what you're doing.

In a study published a decade ago, Meyer and his colleagues found that, contrary to popular belief, people are less efficient—not more—when they multitask. That's because it takes more time to complete one of the tasks, especially as they become more complex, versus focusing on a single task.

How multitasking affects memory and attention
Imagine this: You get off the couch to get a snack from the refrigerator, you're interrupted by a phone call, and arrive in the kitchen with no clue why you're there.

That common scenario illustrates how even the simplest forms of multitasking can lead to glitches in the moment-to-moment processing of information known as working memory, says Adam Gazzaley, MD, an associate professor of neurology, physiology, and psychiatry at the University of California, San Francisco.

These types of distractions are becoming more and more a part of daily life, thanks to computers and smartphones, and research suggests they could be taking a toll on our attention.

In a 2009 study, researchers at Stanford University asked students to take an online questionnaire about their media use. From that group, the researchers identified heavy and light "media multitaskers" and compared their performance on three cognitive tests. Their paper found that heavy media multitaskers had more trouble filtering out irrelevant information from their environment. In others words, they were more prone to distraction than their low-use counterparts. The heavy users were also less able to focus and had more difficulty switching tasks.

It's not clear whether multitasking causes these problems, or if preexisting personal differences make certain individuals more prone to distractions posed by the "changing media environment," the authors note.

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Karen Pallarito
Last Updated: June 23, 2011

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