According to this, you may not be as effective at multitasking as you think you are.
Dr. John Sladky, a professor of pediatrics and neurology at Emory's School of Medicine and the chief of neurology at Emory Children's Center, notes that in visual scans of the brain, the amount of activity diminishes when multitasking comes into play. "A summary of more recent research would indicate that the brain doesn't multitask very well, and unlike a computer that allocates an equal amount of energy for each task, the brain's energy expenditure capability is limited. Simply put, energy for each task is finite."
Interestingly enough, the researchers at the National Institutes of Health are tackling the issue of multitasking through the National Institute of Neurological Disorders and Stroke (NINDS), one of its more than two-dozen research institutes and centers that comprise the government body. Jordan Grafman, chief of the cognitive neuroscience section at NINDS, defines multitasking as working on "a number of different tasks within a short time period." These tasks can be interwoven in an overlapping fashion, by handling a bit of one job and then going back to handle a bit of another, or certain tasks can be completed at the same time, such as participating on a conference call while answering email.
Grafman's research includes work on charting the area of the brain—the anterior frontal cortex—responsible for multitasking behavior. This area of the brain is also one of the most evolved, he notes. Grafman adds that multitasking appears to be a uniquely human ability. "There are individual differences, and an astute manager may pick out who to assign these sorts of tasks to, and those not as well equipped to handle it." However, everyone seems to reach some sort of boiling over point—and that's why an employer needs to be constantly aware of his or her employee's capabilities and current work situation.
More importantly, Grafman's work indicates that performance declines when people do multiple tasks. Then, he notes, "a manager would need to ask themselves if they can accept the standard of work being produced. If the standard is low, then it doesn't matter as much. But if you're worried about performance, then this may not be the answer. We all have limits." Grafman adds that the stress induced by high levels of multitasking, or even other major causes of stress, can "cause a chain reaction in the brain to kill off neurons." Short-term memory loss is a common result. "It is basically short term and it is reversible if not under the stress. But if the stress is persistent, it can be problematic."
I've always been a multitasker. But as more and more neuroscience research has shown that it is ineffective, I've tried to cut it out. Instead of doing two things at once, I get to the point quickly with phone calls and emails and all that stuff so that I can move on (and fully focus) on the next thing.