How we multitask

Gregory Nemec

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Henry Ford intuited a fundamental truth about humans and multitasking: doing several things at once is not our forte. That, after all, is why his factory assembly line, in which each worker concentrates on one task, created vast gains in efficiency. But Andrew Leber, who recently completed a four-year postdoctoral psychology research fellowship at Yale, says there has long been "some evidence that we have periods of time in which we're better at multitasking."

Leber and his colleagues -- Marvin Chun, director of Yale's Visual Cognitive Neuroscience Laboratory, and graduate student Nicholas Turk-Browne -- recently set out to determine whether any particular pattern of brain activity characterizes these periods. They took fMRI scans of volunteers performing two different numerical tasks. For one task, subjects were asked whether each digit in a series was greater or less than five. For the second, they had to say whether digits were odd or even.

The scientists analyzed the subjects' brain activity moments before the tasks were presented and then assessed how efficiently subjects could switch between tasks -- an example of multitasking. When certain brain regions -- the basal ganglia, the anterior cingulate cortex, and parts of the prefrontal and parietal cortices -- were more active, subjects were better at subsequent multitasking. (The study appeared in the September 9 issue of the Proceedings of the National Academy of Sciences.)

These brain areas had previously been implicated in cognitive control, says Leber, now an assistant professor of psychology at the University of New Hampshire. "We could certainly speculate that maybe when your cognitive control network is not as active -- when you're daydreaming or something like that -- your multitasking ability might not be good," he says.

Leber next plans to investigate whether there are particular times of day when we multitask more, or less, efficiently. But the results are preliminary. Unfortunately for the stressed multitasker, says Leber, "it's a bit premature to give a real recommendation."