We call those high multitaskers ... who are constantly using many things at one time when it comes to media. So let's say they're doing e-mail while they're chatting, while they're on Facebook, while they're reading Web sites, while they're doing all these other things. And low multitaskers are people who really are more one-at-a-time people. When they're texting, they're texting. When they're reading a Web site, they're reading a Web site. So those are the low multitaskers.

It turns out multitaskers are terrible at every aspect of multitasking. They're terrible at ignoring irrelevant information; they're terrible at keeping information in their head nicely and neatly organized; and they're terrible at switching from one task to another.

And when people started a third task, one of the original goals disappeared from their brains,

What that suggests, the researchers say, is that multi-task are more easily distracted by irrelevant information. The more we multi-task, the less we are able to focus properly on just one thing.

we've become habituated to checking e-mails and texts, and turn towards the "safe novelty" of Facebook rather than the important but tricky stuff of real life.

Indeed, media multi-tasking sounds, at first glance, like a boon for productivity. If we can do two things at once, we can do twice the amount in the same length of time, or the same amount in half the time

Nass is skeptical. In a recent unpublished study, he and his colleagues found that chronic media multitaskers—people who spent several hours a day juggling multiple screen tasks—performed worse than otherwise similar peers on analytic questions drawn from the LSAT. He isn't sure which way the causation runs here: It might be that media multitaskers are hyperdistractible people who always would have done poorly on LSAT questions, even in the pre-Internet era. But he worries that media multitasking might actually be destroying students' capacity for reasoning.

is whether media multitasking is driven by a desire for new information or by an avoidance of existing information. Are people in these settings multitasking because the other media are alluring—that is, they're really dying to play Freecell or read Facebook or shop on eBay—or is it just an aversion to the task at hand?"

But those scholars also became intrigued by the range of individual variation they found. Some people seemed to be consistently better than others at concentrating amid distraction. At the same time, there were no superstars: Beyond a fairly low level of multitasking, everyone's performance breaks down. People can walk and chew gum at the same time, but not walk, chew gum, play Frisbee, and solve calculus problems.