Science Talk

The Teen Brain; Flipping Magnetic Poles; What's Pluto?

In this episode, journalist Leslie Sabbagh discusses the teen brain, the subject of her cover story in the August/September issue of Scientific American Mind. Geologist Kip Hodges, the director of the Arizona State University School of Earth and Space Exploration, answers a listener's question about the earth's fickle magnetic poles. Plus we'll test your knowledge about the status of Pluto and other science in the news. Websites mentioned on this episode include and

Welcome to Science Talk, the podcast of Scientific american for the seven days starting August 30th. I am Steve Mirsky. This week on the podcast, we're going to talk about one of the most mysterious objects in the universe, the teenage brain. We'll have the first installment of a new segment, "Ask a Scientist" and that's going to be about the earth's magnetic poles flipping around and speaking of flipping around we'll have the latest Pluto status update and we'll test your knowledge about some other recent science in the news, too.

First up journalist, Leslie Sabbagh, she is the author of the cover story in the current issue of Scientific American Mind magazine about the teen brain. I called her at her home in Cleveland.

Steve: Hi Leslie, how are you?

Sabbagh: Hello Steve, I'm fine, thanks. How are you?

Steve: I'm okay. So tell me about the teenager's brain; is it really different from an adult's brain?

Sabbagh: The research shows that it is. It shows that when teens are performing certain tasks that they work much harder using their decision-making prefrontal cortex areas of the brain than adults do; and that means that they are recruiting so much of that portion of the brain—that is, another stressor is added in a particularly challenging situation—that they can't handle that load.

Steve: What do you mean by another stressor?

Sabbagh: Well! Say it['s] driving or say they are performing a complex task—driving is a good one—and a car in front them suddenly slams on the brake, and they are following may be too closely; if they are talking on the cell phone, they may not be able to process all that information as rapidly as an adult and may miss the brake pedal, may not react fast enough, may do any number of things that experienced older drivers wouldn't do.

Steve: And this is actually related to structural business going on in the prefrontal cortex?

Sabbagh: Researchers believe that, yes. They believe that an adult brain recruits more of the whole total brain than adolescents do, so that some of the prefrontal cortex would be occupied with the decision making, but an adult brain recruits other parts, different parts of the brain to help in making decisions; that takes the load off the prefrontal cortex, allows it to handle other inputs or stressors as they come in.

Steve: So multitasking for a teenager is really a bad idea.

Sabbagh: Yeah.

Steve: (laughs) and But they do it all the time, right?

Sabbagh: Yes, they do.

Steve: What ages are we talking about? Is it really set like, you know, 12 years and 3 months to 18 years and 4 months? Or is there some variability on either side?

Sabbagh: Yeah, it's not that structured. The studies looked at adolescents—I believe they were from a 11 to about 17—and they found that age group got better as they got older in recruiting other parts of the brain. But what happens is that, as the brain matures, there is a process called synaptic pruning that goes on and that means that the brain is getting rid of unnecessary neuronal connections—connections between nerves—and that speeds up processing. So this goes on throughout early adult life and this was surprising to some of researchers that into their early 20s in fact the brain was still maturing and getting rid of that extra neuronal material and adding a faster process to the axon—the delivery of the impulse to the nerves—by weighing down more of the matter that help the transmission of those electrical signals.

Steve: That's really interesting; most people might assume that the process by which the brain matures would be to add more connections, but you're actually talking about taking away connections that can confuse the issue.

Sabbagh: Yeah, they are not necessary. The brain adds a lot of neuronal tissue throughout adolescence and it starts pruning it back—[the process is] called synaptic pruning—because it's unnecessary. The brain at that point starts molding itself to the environment so to speak. It is a necessary process, because it adapts itself to its environment.

Steve: There is some controversy and you get into it in the article where some people—just—some researchers just don't think that this idea of a different brain for teenagers really holds water.

Sabbagh: These scientists don't have any experiments to drawn [on], but they cite other research; they cite research that's fairly old and I haven't seen any experiments that['s] based on to point out their opinions, but it's necessary to cover those as well.

Steve: The people who don't believe in the teen brain, they don't deny the results of the experiments that have looked at the structure of the brain, they just don't think that those structural issues account for as much behavioral differences, as the other researchers do.

Sabbagh: It's hard to get your hands around what they naysayers really believe because they cite other research and they don't point to their own experiment, so it's hard to get a real grip on their series[theories]. But the underlying cause is that it's impossible to monitor or to determine a teen brain, because society molds the brain from birth.

Steve: And they point to multicultural studies or multicultural behavior where they say teenagers in other cultures don't have the same kind of issues that American teenagers do?

Sabbagh: Yeah, they do that and they contend that the problems that with decision making or with behavioral outbursts that teens are usually accustomed to having a word, accustomed to seeing, don't occur in other societies because the societies have different expectations and raise their teens and raise their children differently. There is no experimental evidence to show that that is true, but it is an interesting point and hard to prove.

Steve: Hard to prove and hard to disprove; it's mostly just observational and anecdotal.

Sabbagh: Yeah.

Steve: Are there any kind of policy implications for these studies? You know, should the driving age be reconsidered, [or the] drinking age?

Sabbagh: Well that's an interesting concept. You'll find that neurosurgeons—neuroscientists, excuse me—will tell you that it's very difficult even for in a fully formed adult brain to say, drive and carry on a conversation on a cell phone; that if they had their way, they ban all conversation while driving—on cell phones not with passengers—and they, to a person, suggest that teens be not allowed to drive and talk on a cell phone at the same time. But I don't know [what] the implications for policies are; yeah, [that's a] much thornier issue. I don't know that you would get that kind of legislation passed, but probably it would be a lot safer, I think they would all agree. It's just too much input.

Steve: And you touched on something briefly; I am sure listeners are thinking, well, what's the difference between talking on a cell phone while you're driving or talking to a fellow passenger? But there is a difference.

Sabbagh: There is. The fact is that a fellow passenger can also observe the situation in a car, and say there is an emergency situation, the passenger will stop talking and allow the driver to, you know—that will give the driver the time to react appropriately. It's much different with a disembodied conversation; and the conversation is right in your ears, the verbal input is right there and of course you are the [other] participant in the conversation can't see what's going on in the car; see you are getting, the driver would still be getting verbal input while the emergency or the sudden action occurred and [the other participant] couldn't help by stop[ping] talking.

Steve: One another thing about the article is that the author's note in the article and it mentions that you've been in Iraq recently. What were you doing there?

Sabbagh: I am a medical journalist by training and I was very fortunate. I had the great good fortune to fly with the 50th Medical Company, the 101st Airborne who did the medevac in the Baghdad area, so I ended up flying up for [three-and-a–half] weeks with the 50th Medical Company, a great, great group of people. We took up causalities from the point of wounding and the care that they received was amazing, kept them alive.

Steve: And you have any plans to go back?

Sabbagh: I would love to. I would love to go back and follow the Marines this time. The Navy Carmen. The marines love their Navy Carmen—those are the medics for the marines and those people travel on the ground [and] are in much more dangerous situations than I was running into. I am in training for that. I would love to write their story.

Steve: Leslie thanks very much. The article is "The Teen Brain Hard at Work", and then (laughs), and there is a little subhead that says "No Really!", and that's in the current issue of Scientific American Mind. Thanks very much.

Sabbagh: Thank you.

Steve: Leslie Sabbagh's story number on the teen brain is in the August/September issue of Scientific American Mind Magazine, that's at news stands; also available at; and you can read her Iraq coverage online—just Google Leslie Sabbagh, that's S-a-b-b-a-g-h, and it's the first stuff that comes up. Now its time to play TOTALL.......Y BOGUS. Here are four science stories but only three are true. See if you know which story is TOTALL.......Y BOGUS.

Story number 1: Sunscreens can actually damage the skin.

Story number 2: A large store chain is selling a kid's T-shirt that says "Enough With The Learning Already" in their back-to-school sale.

Story number 3: The thing called Pluto gets to stay a planet.

And Story number 4: Physics Nobel Laureate, Frank Wilczeck, made his opera debut last week in Austria.

We'll be back with the answer. But first ... Tired of searching the Internet in a vain attempt to enter your science question[s]? Well you can now "Ask a Scientist." Daren Monroe of Fort Wayne, Indiana wants to know:

Monroe: If and when the polarity of the earth's axis flips, will north become south and how will that affect compasses? Will the needle point to the "S" instead of the "N," and will we become known as the land down under instead of Australia?

Steve: To find out I called Kip Hodges. He was a guest on the July 26th podcast and he is the founding director of the New School of Earth and Space Exploration at Arizona State University.

Hodges: Now that's a really interesting question. Indeed magnetic polarity on Earth does change from time to time; it does look like it changes with a frequency on the order of maybe 200 or 250,000 years. At this point as best we can tell from geological records, so it's not something that—a it's rare, it's something that we do see time and again and if one of these occurs, indeed and we are around the seat—indeed the situation will be that [the] compass points in the opposite direction, the north arrow actually pointing towards what used to be the south magnetic pole. It's important to understand that the magnetic pole is always moving every year—there is a drift in [the] magnetic pole—so every year your compass actually changes its orientation when it points if you were to hold it exactly in the same direction from one year to the next, it's going to change, but you probability won't be able to perceive it, particularly if you live in sort of middle latitudes like we live here in United States. So it’s a constantly changing thing, but the flips are more catastrophic processes and they probably have to do with the interaction between the molten outer core of the earth, which is sort of a constantly moving liquid metal. In fact and the material surrounding the inner core, which is more rigid, and the lower mantle which is also rigid. So although we don't know exactly when a flip in the magnetic pole is going to occur, we do know that they have occurred in past. But the good news here is if you are trying to find yourself with a compass, if you are trying to find your way with a compass, you don't have to worry about it flipping catastrophically or you are on your traverse some place because it does appear to take quite a while for the magnetic poles to flip on a planet, probably order of tens of thousands of years. So it's not going to be something that happens overnight or in five-minute period, but they are things that it appears to be inevitable, that at some point our polarity[ies] flip.

Steve: What's the geological evidence for past flips?

Hodges: Our best record of magnetic changes in magnetic field polarity on our planet is in volcanic rocks for which we know the ages quite well. And whenever a volcanic rock crystallizes, the magnetic minerals in that rock have a certain orientation—crystallized in certain orientation—that's related to the magnetic dipole in the plan. And so we actually see reversals and the orientation of those minerals with time and therefore can make a sequence of magnetic reversals for a time. Actually the development of that sequence of magnetic reversals was the key in the development of plate-tectonic theory; [it] actually gave us the capacity to look at magnetic reversals on [the] seafloor and really then understand that there were certain parallels of the way that magnetic field reversal is distributed on the seafloor that in a sense [serve as] a trap or record of seafloor strength.

Steve: And as far as the northern hemisphere becoming the land down under, that's just a matter of convention?

Hodges: Absolutely.

Steve: Send your science questions to, and if we pick your science question, tell me what they wo[i]n? An answer to your science question from an actual scientist; plus you will have you ask the question yourself on the podcast. So send you[r] science questions to Now it's time to see which story was TOTALL.......Y BOGUS. Let's review the four stories.

Story number 1: Sunscreens can actually damage the skins.

Story number 2: Stores selling back-to-school T-shirts that say, "Enough With The Learning Already."

Story number 3: Pluto is still a planet.

And story number 4: Physics Nobelist sings opera.

Time's up.

Story number 4 is true. Frank Wilczek, winner of the 2004 Nobel Prize in Physics and our guest on the May 3rd podcast, made his operatic singing debut last week in Austria. The asymptotic freedom fighting baritone played the Oxygen Atom in an opera titled "Atom and Eve". You can read more on the blog of his wife, Betsy Devine—that's and don't miss the great photo of Frank Schar, totaled by a fallen tree in New Hampshire. Gravity—not just a good idea. It's the law.


Story number 2 is true. I am looking at the flyer right now that was in the Sunday paper advertising a large chain store's back-to-school sale, (paper rumpling noise) that's the flyer, featuring a T-shirt that says "Enough With The Learning Already". I am not saying which store it is because I don't want to cause a run on these stupid things and I am including this as a science story because you should keep learning science, you rotten kids—what, you want to drive your teacher to suicide? (laughs) You don't wear that to school. You don't wear it to school on the first day of school. (laughs) Now let me tell you what might be funny; what might have made this a little clever. Maybe up spell one of the words wrong in "Enough With The Learning Already" that you wear on your T-shirt to the first day of school; or if the teacher is wearing that T-shirt on the first day of school, that might be funny. But what isn't funny is when you're pumping $6-a-gallon gas into the spiffy new hybrid vehicle of the guy who didn't think he'd had enough with the learning already. Okay, I'm done.

Story number 1 is true. Sunscreens may actually contribute to skin damage. That's according to new research out at the University of California, Riverside. The key is to make sure that a fresh layer of sunscreen is always on the skin, that's the key to protection. If the stuff penetrates down deep enough, UV light hitting the unprotected top layer can cause some chemical reactions that produce compounds that damage the skin much as the UV itself does; and this research will appear in the journal Free Radical Biology and Medicine.

All of which means story number 3 about Pluto remaining a planet is, as you well know TOTALL.......Y BOGUS, because astronomers last week voted Pluto off the island; and that's despite the recommendations of the Planet Advisory Committee of the International Astronomical Union, which we talked about on the August 16th podcast with Richard Binzel, one of the members of that committee. And now everyone's is ticked off because the vote took place on the last day of the conference after most of the 2,500 attendees had left, so only about 430 astronomers were around to decide the issue. Look for the Pluto status to raise its ugly head again in the coming years. Although the definitive definition of what Pluto is can actually be found in the book The Information by Martin Amis; that's on page 55 in the Vintage International edition. I would read it to you, but there may be children in the room. Of course, the really important astronomy story that we had to do with the evidence for the existence of dark matter, and we'll talk about that on next week's podcast.

Well that's it for this edition of the Scientific American podcast; our e-mail address is; and also remember the[at] science news is updated daily on the Scientific American Web site, For Science Talk, the podcast of Scientific American, I am Steve Mirsky, thanks for clicking on us.

Mr. Sun: Hey Pluto, how's it going?

Pluto: Fine. You wanted to see me, Mr. Sun?

Mr. Sun: So, Pluto any chance you['re] going be cleaning out that desk soon?

Pluto: I was told that I would not have to be cleaning out my desk, so I was not planning to clean out my desk.

Mr. Sun: (Hissing noise) Ouch! Yeah, seems like somebody missed a memo. Turns out upper management had IAU going over the TPS reports, and long-shot, is we're letting you go, Pluto.

Pluto: I was told specifically two weeks ago that I was not going to be let go. That the advisory committee ...

Mr. Sun: Yeah, yeah.

Pluto: ... is going to look at things.

Mr. Sun: Yeah, turns out, you and Xena and Ceres are all being reassigned over to dwarf planet status.

Pluto: (mumbles) That is not fair. I have 75 years in and they are only on probation and....

Mr. Sun: Yeah.

Pluto: Consider the whole situation.

Mr. Sun: So, we're going to set you up with dwarf planet status, sort of away from the rest of the planets. And there are no benefits with that position.

Pluto: I'm taking my stapler.

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