From "Multitasking Makes You Stupid: Studies Show Pitfalls of Doing Too Much at Once," by Sue Shellenbarger:
--People who multitask are actually less efficient than those who focus on one project at a time, according to a study published in the Journal of Experimental Psychology. The time lost switching among tasks increases with the complexity of the tasks, according to the research by Dr. Meyer and others.You can read the Wall Street Journal article by clicking here.
--The process of switching back immediately to a task you've just performed, as many multitaskers try to do, takes longer than switching after a bit more time has passed, say findings published last fall by researchers from the National Institute of Mental Health. The reason is that the brain has to overcome "inhibitions" it imposed on itself to stop doing the first task in the first place; it takes time, in effect, to take off the brakes. If you wait several seconds longer before switching tasks, the obstacles imposed by that shutting-off process are reduced.
--Managing two mental tasks at once reduces the brainpower available for either task, according to a study published in the journal NeuroImage. Marcel Just of Carnegie Mellon University asked subjects to listen to sentences while comparing two rotating objects. Even though these activities engage two different parts of the brain, the resources available for processing visual input dropped 29% if the subject was trying to listen at the same time. The brain activation for listening dropped 53% if the person was trying to process visual input at the same time.
"It doesn't mean you can't do several things at the same time," says Dr. Just, co-director of the university's Center for Cognitive Brain Imaging. "But we're kidding ourselves if we think we can do so without cost."