TOPICS > Science

The Teen Brain

October 13, 2004 at 12:00 AM EDT


BETTY ANN BOWSER: Matt and Adam Bukowski toured the Air and Space Museum in Washington recently with their parents. Although they are average teenagers, these 14-year-old fraternal twins are on the cutting edge of brain science.

MATT BUKOWSKI: I play soccer. I’m just more like flexible than him and…

BETTY ANN BOWSER: Who has more girlfriends?

(Adam raising hand)

MATT BUKOWSKI: I think, me. I think I do.



BETTY ANN BOWSER: It’s because they’re twins and normal teenagers that the Bukowskis are interesting to Dr. Jay Giedd at the National Institute of Mental Health. Thirteen years ago, he and his colleagues began using magnetic resonance imagery to open a window into the brains of ordinary teenagers like Matt and Adam.

He chose twins as a good way to show how genes and the environment affect brain development. His findings not only show that young brains are physically different from adult brains, but they function differently too. Now some of that science is being used outside of the lab to try to get this young man off of Death Row.

Christopher Simmons was a 17- year-old high school junior when he was charged with the murder of Shirley Crook near St. Louis in 1993. He quickly confessed to breaking into Crook’s home intending to rob her. Then, he said, he panicked, tied her up and, with a 15-year-old friend, pushed her off a railroad trestle. Simmons’ classmates had trouble connecting such a brutal crime to the kid they thought they knew.

HIGH SCHOOL STUDENT: He talked and acted like he was a hot shot every once in a while, but pretty much he was quiet.

HIGH SCHOOL STUDENT: From what I knew he looked a pretty good guy. I didn’t think he’d do what he did.

BETTY ANN BOWSER: Simmons was tried as an adult and sentenced to death. Now brain science has become central to his fate. The Simmons case is in the hands of the U.S. Supreme Court after Missouri’s highest court overturned his sentence, saying the execution of a 17 year old was cruel and unusual punishment. A brief filed by eight medical and mental health groups quotes Giedd’s work, among others, to claim that adolescents are immature in the very fibers of their brains, so 17 year olds shouldn’t have full criminal responsibility for capital crimes.

Mark Wellek, a psychiatrist in Phoenix, helped initiate that brief.

DR. MARK WELLEK, Psychiatrist: We have some new brain science evidence that says brains aren’t well developed, they’re not finished developing, especially the part that helps control impulses. And the part that sends out lots of impulses: Cover yourself, protect yourself, don’t let this lady know who you are, do something about it. It’s the part of the brain that says “protect yourself” — sends out big signals — and those don’t get slowed down or managed by the front of the brain called the prefrontal cortex, because it’s not developed yet.

BETTY ANN BOWSER: Psychologists have been studying adolescent behavior for decades. The basic findings flesh out what parents know by instinct: That teenagers can act like kids one day, adults the next, and sometimes have trouble overriding their impulses. In the past, that behavior was blamed on hormones. Wellek’s brief tries to show that adolescent behavior has a physical basis in the brain. It quotes Giedd’s work to show that the gray matter, the brain cells that actually think, continue to builds up to about age eleven or twelve. After that, the connections between individual nerve cells begin to thin out as the brain matures. But Giedd says different parts of the brain mature at different times.

DR. JAY GIEDD: Here are the parts that are motor and sensory and touch and then this particular part involved in impulse control, decision making, fills in last, and so that’s been the seed of a lot of judicial and educational and even social implications.

BETTY ANN BOWSER: The twins in Giedd’s study return for new scans every two years. This is the Bukowskis third visit. Newcomers, like seven year olds Bailey and Taylor Ewing, begin with a series of tests for things like attention span and memory. They go through two brief calibration scans, then a ten- minute scan, the so-called “money shot” that produces a detailed brain image.

While Giedd’s work focuses on brain structure, Abigail Baird at Dartmouth is working on behavior. She uses typical public school students like 14-year-old Tim Warren and his 12-year-old sister Melinda. Her focus is on how teenagers make decisions.

ABIGAIL BAIRD: Jane and I are going to give you guys some scenarios. And what we want to do is– we’ll do a show of hands as to whether these things are good ideas or bad ideas. Okay? Doing the laundry. Good idea, bad idea? How many people think it is a good idea? How many people think it is a bad idea?

JANE VINER: Okay. What about riding your bike down a staircase?

ABIGAIL BAIRD: How many people think it is a bad idea? How many a good idea? Okay. How about swallowing a cockroach. Good idea? How many people say a good idea, swallowing a cockroach?

BETTY ANN BOWSER: Behind the apparently silly questions, there’s the serious science of how teen brains work when their owners try to make simple judgments about safe or dangerous activities. While the scanner pictured their brains, they answered the good idea/bad idea questions. Baird also asked adults the same questions.

ABIGAIL BAIRD: Doing the laundry, is that a good idea or a bad idea?


ABIGAIL BAIRD: Okay, swallowing a cockroach?



BETTY ANN BOWSER: Baird found that adults and teens both knew, for example, that swimming with sharks wasn’t such a good idea. But on their brain scans, adults used the part of the brain that processes visual imagery to form answers.

ABIGAIL BAIRD: When I asked you about the cockroach, did you have a picture of a cockroach in your head?


ABIGAIL BAIRD: And did you get a little pang of, like, ick, a little yuck?


ABIGAIL BAIRD: Okay. So what happens is that in these scenarios adults have a system, an automatic system, for processing these types of dilemmas where we instantly get a visual and we instantly, if it is dangerous or gross or aversive, we get that pang.

BETTY ANN BOWSER: Teens sometimes came up with different lines of reasoning to reach their conclusions.

ABIGAIL BAIRD: Has anyone actually ridden their bike down the stairs? That’s a startling number of people. What were you thinking? Someone tell us what they were thinking when you were riding. I mean, did you get hurt when you did it?

GIRL: No, it was like five stairs so it wasn’t too much. But it was kind of interesting. It was fun.

BETTY ANN BOWSER: Baird says, regardless of their conclusions, teens used a different part of their brains, farther up front, to think about the problem.

ABIGAIL BAIRD: What we found is they actually use their frontal cortex, the cognitive part of their brains. They are actually trying to think about this. They are trying to reason about this and it is not automatic. It is very labored for them.

BETTY ANN BOWSER: Though the work of Baird and Giedd is cited in the Supreme Court brief, neither had a hand in writing it. And both have reservations about some of the reasoning.

DR. JAY GIEDD: That’s been an issue that we’ve gone around and around with in terms of the utilization of these images and what we can say from the science standpoint is that “yes, the brain of a 16 year old is different than the brain of a 25 year old.” But what should that mean for the judicial system or other systems? I think that it’s just too great of a leap at this point.

BETTY ANN BOWSER: Are you satisfied that there is enough science there to make some of these pronouncements?

ABIGAIL BAIRD: No, not yet. I think there is enough science there to make a big question mark about what we are doing or about some of the policy that is out there.

BETTY ANN BOWSER: Like the death penalty?

ABIGAIL BAIRD: Yes, I think we have to be extremely careful in how it is applied because it’s not our business to tell people what to do.

BETTY ANN BOWSER: Wellek, though he’s not directly involved in the brain research on teenagers, still thinks the evidence is clear enough to oppose the death penalty for 17 year olds.

DR. MARK WELLEK: I don’t know that absolute proof will ever come of this kind of thing, but every piece of science that’s being done now seems to move in that direction. There’s not been one single piece of science that moves in another direction and disproves that.

BETTY ANN BOWSER: Before Giedd’s work began, most scientists believed the brain was a finished product by age 12. But the findings from brain imaging show the brain takes much longer to mature and doesn’t fully mature till about 25. Some are predicting those findings have the potential to redefine the meaning not only of adolescence but adulthood too. The Supreme Court case may be only the beginning of that process.