The Thief of Time
Multitasking is Inefficient, Studies Show

audioListen to Joanne Silberner's report

audioHost Renee Montagne tries hard to talk about multitasking

August 6, 2001 -- "To do two things at once," said the Roman sage Publilius Syrus, "is to do neither." And this was 2,000 years ago, long before people tried to drive while talking on their cellphones and digging for tollbooth change and yelling at the kids and (ahem) listening to the radio.

David Meyer
David Meyer
Photo courtesy of David Meyer
Syrus may have overstated the case, but a new study concludes that performance does drop off when people try to accomplish more than one task at a time. Another sage -- William Shakespeare this time -- called procrastination "the thief of time." But it looks like multitasking is giving procrastination a run for its money.

Professor David Meyer of the University of Michigan and his colleagues set out to measure the effects of multitasking. They asked several dozen student volunteers to switch back and forth between different types of arithmetic problems. If they had to switch rapidly from, say, multiplication to division, it took them "quite a bit" longer to finish, Meyer said.

For instance, it might take a minute to finish 10 multiplication problems, but a mix of 10 multiplication and division problems might take 15 or 20 seconds longer.

Professor Marcel Just of Carnegie Mellon University said there is a drop-off in efficiency even when different parts of the brain are used for different tasks. Just used a brain-imaging machine
Marcel Just
Marcel Just
Photo courtesy of Carnegie Mellon University
to see what part of the brain that test subjects used when they listened to complicated sentences while simultaneously looking at a geometric object they were told to mentally rotate. Just had expected that the different parts of the brain wouldn't be affected by what the other part was working on. Or, he thought, each part might have to work harder to complete its task. Instead, it turned out that both parts of the brain worked less efficiently, meaning that less brainpower in total was directed at both tasks than would have been used if only one task were attempted at a time.

Meyer has done studies concluding that people can, through training, improve their ability to multitask. He calls this "mental yoga." For instance, with practice, people can improve the time it takes them to respond to a visual prompt on a computer while also reacting to auditory prompts through headphones.

But Meyer says there's a limit to the improvement, and that workers -- and bosses -- tend to overestimate the ability to multitask. His advice: "If you can avoid it, don't multitask."

And, for the record, both Meyer and Just oppose talking on the phone while driving, except in the safest driving conditions -- well-known roads with little traffic, and no tollbooths.

Other Resources

audio In this audio feature from All Things Considered last fall, commentator David Weinberger argues that slicing your attention is like slicing a plum -- you lose some of the juice.

Technology is the prime reason for our increasingly multitasked lives. We do it because, thanks to our gadgets, we can. But does that mean technology is to blame? In her 1999 examination of three books on the subject by James Gleick, Douglas Rushkoff, and David Shenk, Salon's Janelle Brown asks whether the problem is technology or our failure to wisely adapt to it.

Consultants Michelle Weil and Larry Rosen offer tips for coping with "Multitasking Madness" in a 1998 article in Context magazine.

Check out the University of Michigan psychology department's Brain, Cognition, and Action Laboratory home of David Meyer's research, where the goal is "developing an accurate and precise Universal Theory of Cognition."

And finally, Carnegie Mellon's Center for Cognitive Brain Imaging, where Marcel Just is co-director.