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Busy brain. Juggling various media modes may leave us befuddled.

Multitasking Muddles the Mind?

Bad news for people who like to text their BFFs while surfing the Web for some new shoes and watching the latest episode of Project Runway. Scientists who've conducted what they say is the first-ever study of chronic multitaskers found that cognitive performance declines when people try to pay attention to many media channels at once.

Although media multitasking has become more and more prevalent, no one knows how chronic media immersion affects cognitive functioning. So a team headed by psychologist Eyal Ophir of Stanford University in Palo Alto, California, identified 19 "heavy media multitaskers" (HMMs) and 22 "light media multitaskers" (LMMs) among a group of students based on how often they reported simultaneously using media such as television, cell phones, computer games, and videos.

The researchers then gave subjects in the two groups tests to see how well they could sift relevant information from the environment, filter out irrelevant information in their memories, and quickly switch between cognitive tasks. One filtering test, for example, required viewers to note changes in red rectangles while ignoring changes in blue rectangles in the same pictures. In the task-switching experiment, participants were presented with images of paired numbers and letters and had to switch back and forth between classifying the numbers as even or odd and classifying the letters as vowels or consonants.

The HMMs did worse than the LMMs across the board. Surprisingly, says co-author and sociologist Clifford Nass, "They're bad at every cognitive control task necessary for multitasking." They were more easily distracted by irrelevant stimuli, and although their memories were no worse than those of theLMMs, they had more difficulty in selecting stored information that was relevant to the task at hand. In one filtering test, for example, the LMMs took 323 milliseconds to discern the correct answer, but the HMMs averaged 400 milliseconds.

Nass says the study has a disturbing implication in an age when more and more people are simultaneously working on a computer, listening to music, surfing the Web, texting, or talking on the phone: Access to more information tools is not necessarily making people more efficient in their intellectual chores. Also disconcerting, he notes, is that "people who chronically multitask believe they're good at it." The findings are reported this week in the Proceedings of the National Academy of Sciences.

Daphne Bavelier, a cognitive scientist at the University of Rochester in New York state, says the research presents a puzzle about the brain's ability to learn from experience. Bavelier has discovered that people who play action video games get better at the kind of task-switching those games require. In contrast, Bavelier says, the poor performance of multitaskers in the new study suggests that more experience doesn't always translate to improved performance.

It's still not clear, however, that multitasking really scrambles the brain. It's also possible that people with poor filtering and attentional abilities are more prone to multitasking to begin with. Anthony Wagner, a psychologist in the Stanford group, says he suspects that constant jumping among different media offers instant rewards that reinforce "exploratory" behavior at the expense of the ability to concentrate on a particular task.