Dragons. Leprechauns. Fairies. Zeus. Multitasking.

What does multitasking have to do with these other myths? According to psychiatrist Richard Hallowell, multitasking is “mythical activity in which people believe they can perform two or more tasks simultaneously.” We actually lose 10 IQ points when we attempt to do two things at once, more than double the drop that occurs when someone smokes marijuana. This is the equivalent of missing one night’s sleep.

Here’s another myth about multitasking: it helps us get more done at once. In fact, multitasking slows us down. Multitasking increases the levels of stress-related hormones such as cortisol and adrenaline, and it disrupts the regions of the brain related to memory and learning. “We are using our mental energy to concentrate on concentrating at the expense of whatever it is we’re supposed to be concentrating on,” says Walter Kirn.

Another myth? Ms. Jones can’t multitask any better than Mr. Jones. Increased options available to women have led to an increased need for multitasking, but she’s no better at it than her male counterparts. The fact that she has to plan dinner while checking homework on her way home from work does not mean she’s doing a good job at it.

At this very moment I have seven windows running on my computer, ten open websites, the television is blaring and I’m talking to my mother-in-law. How many things are you doing? Why did you switch between activities? What would happen if you concentrated on one task until it was completed? What if that task was talking with your kids without checking your email on your cell phone? Would that be good? How can you help Ms. Jones remain focused when she’s trying to do business with you?

Supercomputers can multitask. Homo sapiens can’t.