Trying to save time? Do one task at a time.

Think you're saving time by preparing dinner, balancing your checkbook, and helping Junior with his Algebra homework all at the same time? Well, studies say, "Not so fast."

Researchers at the University of Michigan and the Federal Aviation Administration have found that working on several tasks at the same time can take two to four times longer than if you try tackling them one after the other. Brain-scan studies help explain why: When you try to do two or more things at once, your brain constantly switches back and forth between the tasks, a less efficient use of your neurons. Sleep loss, stress, and mood disorders can worsen the problem.

So fight the urge to multitask and try to do just one thing at a time.