Professor Earl Miller of MIT studied the brain activity of volunteers as they performed several different tasks simultaneously. That study revealed that, though the volunteers were appeared to be focusing on all tasks at once, their brains had actually zeroed in on only one or two tasks at a time.

The study found there was minimal brain power being exerted for each task, and the power that was being used, came in brief, unproductive spurts. (From the NY Daily News - Stop the multi-tasking madness! Attempting to do it all can cause neurological damage: studies by Issie Lapowski.)

Multi-tasking like this also makes learning new information virtually impossible. A study by Professor Russell Poldrack, a psychologist at the University of California, compared the brain function of people who study with a distraction, like the TV, to people who study with no distractions.

He found that the information the distracted participants studied actually traveled to a different part of the brain than the information the other volunteers studied.

“We found that a key limitation to efficient multi-tasking is the speed with which our prefrontal cortex processes information, and that this speed can be drastically increased through training and practice,” according to Paul E. Dux, a former research fellow at Vanderbilt, and now a faculty member at the University of Queensland, Brisbane, Australia.

Before practice, the participants showed strong dual-task interference, a slowing down of one or both tasks, when they attempted to perform them together. However, as a result of practice and training, the individuals became quicker at doing each of the two tasks separately and also at performing them together effectively becoming efficient at multi-tasking.

The MRI data indicated that these gains were the result of information being processed more quickly and efficiently through the prefrontal cortex. (From PhysOrg.com - Training can improve multi-tasking ability by Melanie Moran.)

For individuals who must perform multiple tasks in rapid succession or concurrently, it is recommended that your first train yourself to perform individual tasks separately and then together. The result should be an overall improvement when putting them all together. 

      It seems to be physically impossible to reach a point where a brain can sub-consciously “chunk” the information (data) processing into such small pieces that approach true multi-tasking of an inorganic computer.

      When attempting activities requiring concentration, avoid multitasking and interruptions, research shows it takes us at least 20 minutes to regain our previous concentration level after an interruption. Check out the Information Overload Research Group.