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SCIENCE OBSERVER

Multitasking to Distraction

Users of many concurrent media streams actually are less able to switch between tasks

Fenella Saunders

Children studyingClick to Enlarge ImageIn this era of media bombardment, the ability to multitask has been seen as an asset. But people who commonly have simultaneous input from several types of media—surfing the Web while texting and listening to music, for instance—may in fact find it harder to filter out extraneous information. “We embarked on the research thinking that people who multitasked must be good at it,” says Clifford Nass, a psychologist at Stanford University who studies human-computer interaction. “So we were enormously surprised.”

Nass and his colleagues separated about 100 undergraduate students into groups of heavy and light media multitaskers. Heavy multitaskers commonly have five to six inputs going at once, which could include multiple chat windows as well as other forms of data. The two groups took part in four computerized tests designed to determine their ability to discern information of interest amidst distractions.

For instance, students had to judge whether one of two red rectangles, in a field of blue rectangles, had changed orientation. Another test involved identifying pairs of letters, sometimes with “distractor” letters flashing between them.

A third test asked students if the current letter shown was the same as the one they had seen two or three letters before. Finally students had to classify a number-letter target (such as “b3”) as even or odd, or a vowel or a consonant.

As the researchers report in the September 15 issue of the Proceedings of the National Academy of Sciences of the U.S.A., the tests showed that the chronic multitaskers consistently were more susceptible to interference from irrelevant stimuli. On the test referring back two or three letters, heavy multitaskers had a tendency to produce false alarms on letters they had seen earlier, showing that they were more susceptible to distraction from items that seemed familiar and less capable of blocking from memory data that had become inconsequential.

Surprisingly, the heavy multitaskers also performed more slowly on tests that required them to quickly switch between tasks, as on the letter-number pairs. It seems that they are less able to filter out their knowledge of the previous task and look at things afresh.

The researchers found no overarching cognitive or personality differences between the heavy and light multitaskers.

There is considerable evidence that human cognition is ill suited to multitasking. So why do we work so hard to do it if we’re so bad at it? Nass and his colleagues are planning studies to find out, but they have a couple of competing theories. One possibility is that multitaskers have become so habituated to an onslaught of information that they operate on the assumption that any input is potentially relevant. Another idea is that it’s much like why humans now overindulge in unhealthful foods: Just as we are wired to like sugar and fats, we are predisposed to seek out as much information as possible, particularly about other humans. “It could be that multitasking is just that desire run amok,” says Nass. “What may have been an evolutionary advantage becomes an evolutionary disadvantage when you put it in a world of plenty.”

The motivation to understand multitasking is more than academic. “To the extent it’s attitudinal, we have to change attitudes,” says Nass. “To the extent it’s habitual, we have to change practices.”

All other implications aside, the results already have conferred relief to some. “The biggest reactions have come from nonmultitaskers, who complain about how much they’ve felt alienated for being unable to multitask,” says Nass. “It’s been remarkably comforting to them.”—Fenella Saunders


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