The work could also have "important practical applications to areas such as traffic safety [e.g., air traffic control, or driving while using a cell phone], and neurological disorders such as dementia where the ability to multitask is lost," added Dr. Fatta B. Nahab, an assistant professor of neurology at the University of Miami Miller School of Medicine.
"Knowing our limitations is [being able to] not overwhelm them, so in a business like air-traffic control, you would want to limit the number of tasks everyone is responsible for and divide the responsibilities across those people," Nahab said.
These authors used functional MRI to study the brains of people while they were performing fairly complicated tasks involving letter sequencing.
In the first scenario, volunteers were asked to alternate between two different tasks. In the second scenario, participants were told to postpone one task while completing the other one.
The most surprising finding, Koechlin said, was that when volunteers postponed a task, rather than substituting one for another, the two frontal lobes lit up as they focused on the one task.
Introducing a third task increased the error rate.
"This inferred that the brain was inherently unable to do three tasks simultaneously, so the assumption is because we have two hemispheres [of the brain], we are able to do two tasks at the same time," said Dr. Michael Hutchinson, an associate professor of neurology at NYU Langone Medical Center in New York City.
"It happens as if each frontal lobe is pursuing its own goal!" Koechlin said. "This finding . . . suggests that the frontal function cannot keep track of more than two goals/tasks at the same time."
Stanford University has more on the perils of electronic multitasking
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