To multitask, first brain must practice, practice

VANDERBILT (US)—The reason most people are lousy multitaskers, according to new research, is that our brains process tasks slowly, creating a decision-making bottleneck when multiple tasks compete for attention. Train the brain to perform a task more quickly and multitasking becomes a snap.

“We found that with training, the ‘thinking’ regions of our brain become very fast at doing each task, thereby quickly freeing them up to take on other tasks,” says study coauthor Paul Dux, a former research fellow at Vanderbilt University and now a faculty member at the University of Queensland in Australia.

For the study, researchers trained seven people daily for two weeks on two simple tasks—selecting an appropriate finger response to different images and selecting an appropriate vocal response (syllables) to the presentation of different sounds.

The tasks were done either separately or simultaneously to mimic multitasking. Scans of the individuals’ brains were conducted three times over the two weeks using functional magnetic resonance imaging (fMRI) while they were performing the tasks.

The participants were initially slow to perform one or both tasks when they tried to do them together, but after practice and training, the same participants were able to perform both tasks quickly, when they were done separately and when they were done at the same time. In other words, they became very efficient multitaskers.

The fMRI data shows that these gains were the result of information being processed more quickly and efficiently through the prefrontal cortex.

“Our results imply that the fundamental reason we are lousy multitaskers is because our brains process each task slowly, creating a bottleneck at the central stage of decision making,” René Marois, associate professor of psychology at Vanderbilt and coauthor of the study, explains.

“Practice enables our brain to process each task more quickly through this bottleneck, speeding up performance overall.”

But simultaneous multitasking may actually be a mirage of the mind, the researchers say.

“Even after extensive practice, our brain does not really do two tasks at once,” Dux says. “It is still processing one task at a time, but it does it so fast it gives us the illusion we are doing two tasks simultaneously.”

The researchers note that though their results showed increased efficiency in the posterior prefrontal cortex, this effect and multitasking itself are likely not supported solely by this brain area.

“It is conceivable, for example, that more anterior regions of prefrontal cortex become involved as tasks become more abstract and require greater levels of cognitive control,” Marois says.

The research was funded by the National Institute of Mental Health and appears in the June 15 issue of Neuron.

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