RENEE MONTAGNE, host:
This is Morning Edition from NPR News, I'm Renee Montagne.
ARI SHAPIRO, host:
And I'm Ari Shapiro. Think you're an expert on doing several things at once? Good. Hang on.
Unidentified Man #1: I've got my iTunes. I've my email. I've also got a game.
SHAPIRO: This month in "Your Health," we'll hear about something we all do, even if we don't want to, multitasking. We'll spend some time with teenagers.
Unidentified Man #1: That's extremely lame.
SHAPIRO: We'll also visit a lab to find out what the brain does and fails to do when it juggles many jobs. But first, NPR's Jon Hamilton begins our story in a place where you can hear multitasking, smell it, even taste it.
JON HAMILTON: It's a diner, the Tastee Diner in Bethesda, Maryland.
Unidentified Waitress: One two, one with scramble, one with hash. One rye only.
HAMILTON: To survive as a short-order cook here, you have to keep a half-dozen orders in your head while flipping pancakes, cracking eggs.
Unidentified Waiter #1: Bacon, egg, and cheese bagel.
HAMILTON: Working the counter and refilling coffee cups.
Unidentified Waitress: Half a grapefruit, please.
HAMILTON: They're small tasks. On a busy day though, they can add up to a tough job for Shawn Swinson.
Mr. SHAWN SWINSON (Cook, Tastee Diner): In my first month here I was ready to walk out the door.
Unidentified Waiter #1: Where's my oatmeal?
HAMILTON: And what's it feel like when you're in the middle of rush hour? What's it feel like to...
Mr. SWINSON: It's like you're in an insane asylum. Almost unbearable.
Unidentified Waiter #2: Scrambled ham steak over bacon. One wheat only.
HAMILTON: Swinson has learned to handle the pressure.
Unidentified Waitress: Ready for another one, gentlemen?
HAMILTON: He's an island of calm even when the orders are flying.
Unidentified Waitress: Two orders of mini-chocolate chip.
HAMILTON: But Swinson's boss, Frank Long, says very few people can keep up without losing their cool.
Mr. FRANK LONG (Manager, Tastee Diner): It's the most difficult job in this type of operation. Every table is occupied, four cooks, five waitresses getting them in and out.
HAMILTON: So when does it get the craziest? When the customers are multitasking too.
Mr. LONG: Lunchtime. People may have an errand to run, maybe go to the bank, maybe pick up some dry cleaning, and eat. All say within an hour or whatever allotted time they have.
HAMILTON: It's all part of life these days. We answer emails while yapping on the phone. We schedule appointments while driving and listening to the radio. And it seems as if we're focusing on all these tasks simultaneously, as if we've become true masters of doing 10 things at once. But brain researchers say not so much.
Dr. EARL MILLER (Professor of Neuroscience, MIT): People can't multitask very well. When people say they can it's usually because they're deluding themselves. The brain is very good at deluding itself.
HAMILTON: Earl Miller, Picower professor of Neuroscience at MIT, says for the most part we simply can't focus on more than one thing at a time. What we can do, Miller says, is shift our focus from one thing to the next with astonishing speed.
Dr. MILLER: Switching from task to task, you think you're actually paying attention to everything around you at the same time. But you're actually not. You're paying attention to maybe one or two things simultaneously, but switching between them very rapidly.
HAMILTON: Miller says there are several reasons the brain has to switch among tasks. One is that similar tasks compete to use the same resources in the brain.
Dr. MILLER: Think about writing an email and talking on the phone at the same time. You cannot focus on one while doing the other. That's because a lot of what's called interference between the two tasks. They're a very similar one. They both involve communicating via speech or the written word, and so there's a lot of conflict between the two of them. And they're really nearly impossible to do at the same time.
HAMILTON: Researchers can actually see the brain struggling. And now they're trying to figure out the details of what's going on.
Unidentified Man #2: Just check and see if they're ready for you. Can you hang on one second right here?
HAMILTON: We're at a lab at the University of Michigan in the control room of an MRI scanner. On the other side of a thick pane of glass, a young man is lying face up inside a giant magnet.
Unidentified Woman: OK, we're going to do another quick scan of your brain. You don't need to do anything, just keep your head still.
HAMILTON: The neuroscientist in charge is Daniel Weissman who explains that the man in the scanner will be performing different tasks depending on the color of two numbers he sees on a screen.
Dr. DANIEL WEISSMAN (Neuroscientist, University of Michigan): And if the two digits are one color, say red, the subject decides which digit is numerically larger. On the other hand, if the digits are a different color, say green, then the subject decides which digit is actually printed in a larger font size.
HAMILTON: Got that? If you didn't, maybe it's because these tasks were designed to be tricky.
Unidentified Woman: Great. We're going to go ahead and begin.
HAMILTON: MRI studies like this one have shown that when the man in the scanner sees green, his brain has to pause before responding to round up all the information it has about the green task. When the man sees red, his brain pauses again to push aside information about the green task and replace it with information about the red task.
Unidentified Woman: If you can go ahead and try to respond a little faster for this next round, that would be great.
HAMILTON: If the tasks were simpler, they might not require this sort of full-throttle switching.
Unidentified Woman: All right, here we go.
HAMILTON: But Weissman says even simple tasks can overwhelm the brain when we try to do several at once.
Dr. WEISSMAN: If I'm out on a street corner, and I'm looking for one friend who's wearing a red scarf, I might be able to pick out that friend. But if I'm looking for a friend who's wearing a red scarf on one street corner, and in the middle of the street I'm looking for another friend who's wearing a blue scarf, and on the other side of street I'm looking for a friend who's wearing a green scarf, at some point I can only divide my attention so much.
HAMILTON: So the brain starts switching. Scan for red, switch. Scan for blue, switch. Scan for green, switch. The part of the brain that does this is called the executive system. It's a bit like one of those cartoon conductors telling the orchestra louder, softer, faster, slower. The conductor in our heads lives in the brain's frontal lobes, basically above our eyes.
Dr. WEISSMAN: So, executive processes allow us to make plans for future behaviors. They allow us to exert some sort of voluntary control over our behavior.
HAMILTON: The executive system also helps us achieve a goal by ignoring distractions.
Dr. WEISSMAN: So, for example, if we're performing a task where we want to watch TV and ignore voices that are coming from, I don't know, our children nearby, our frontal regions of the brain may configure the rest of the brain to prioritize visual information and dampen down auditory information.
HAMILTON: And the brain's executive will keep us in that mode until we hear, say, one of our children screaming.
Dr. WEISSMAN: These are things that make us most human. Humans are able to exert free will. We are not like jellyfish. It's not that when you poke us we always do the same thing.
HAMILTON: We're also not like cats, or dogs, or even apes when it comes to controlling how our brain responds and what it responds to. Weissman says this skill probably evolved to help humans who are pretty vulnerable physically do things like hunt animals that are bigger and stronger.
Dr. WEISSMAN: Hunting requires a lot of planning, right? You've got to think about, well, what's that tiger going to do? And I've got my group of friends, how can we coordinate ourselves and surround the tiger?
HAMILTON: And keeping track of all of these things wouldn't be possible without the executive system, that symphony conductor in our frontal lobes.
Dr. WEISSMAN: You know, there are lots of animals in the world that hunt without these increased abilities. So I wouldn't say that to be a good hunter you have to have a lot of frontal development. But on the other hand, it helps, right. This is why humans have become dominant on the planet.
HAMILTON: And perhaps too confident in our own skill. Studies show that we frequently overestimate our ability to handle multiple tasks. For early humans, that sort of miscalculation could have meant becoming a tiger's lunch. These days, the consequences are more likely to be stress, a blunder, or a car crash. Jon Hamilton, NPR News.
SHAPIRO: And Jon's next reports look at the many ways that doing too much can mess with our heads.
Dr. WEISSMAN: It becomes a given that you will be multitasking, so you kind of, before you start, give up trying. You're teaching yourself to give like 10 percent to each thing.
HAMILTON: If you still think you're a champion multitasker - yes you, the one who's drinking coffee while you put on your make-up and chat on your cell phone while you drive - you can compare your skills with Shawn Swinson, the cook interviewed for this story. A video of him at work is at npr.org.