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Monday, September 25, 2006

On the teenage brain

Teenagers have the brain of adults, if one considers size, weight, folds and specialization in regional areas. Yet, there are some subtle but crucial neural differences that make teenagers into those strange animals we all know from Hollywood movies and personal experience.

A recent article by Kendall Powell in Nature magazine (24 August 2006) summarizes research on the neurobiology of the maturing brain that confirms some intuitive knowledge while undermining other common tales about teenagers. For example, folk psychology maintains that girls mature emotionally earlier than boys, and sure enough researchers have found that a crucial process of thinning of gray matter in the brain is completed earlier in teenage girls than boys. This process “awakes” prefrontal regions that are involved in decision making and in balancing emotional and rational inputs, providing a mechanism for the folk psychological observation.

Another interesting finding is that teenagers have a much harder time than adults at even simple tasks that involve controlling one's impulses, but with a twist. For example, when told to ignore a light visible through their peripheral vision, teenagers do as well as adults, but much larger portions of their frontal regions light up during the task. These are the regions involved in rational decisions, and apparently teenagers need to use them in overdrive to keep themselves from yielding to even very simple impulses. Imagine the extra work that teenage frontal regions have to do if the task is to keep away from sex, drugs or alcohol...

Current neurobiology also shows that, interestingly, we really ought not to give up too easily on teenagers. Contrary to the common wisdom that one can influence youngsters up to puberty, and then we simply ought to hope for the best, it turns out that the brains of even first-year college students undergo measurable changes within a span of a few months, changes that can be influenced by the educational environment to which the youngsters are exposed. This may be the last significant developmental window to help our children and students to better reason and integrate their emotional and rational circuits. So much for my many colleagues who think that teaching introductory courses to undergraduates is a waste of time (interestingly, a control group of postdoctoral students – a demographic group slightly older than graduate students – showed no such changes in the structure and activity of their brains...)

The research summarized in the Nature report also explains why people in their '50s are – on average – wiser than younger people. The brain undergoes a process of myelination (i.e., deposit of myelin, the substance that in part makes up the white matter of the brain) beginning with the teenage years. This process allows faster connections among different parts of the brain, sort of like switching from dial-up to broadband internet connection. The augmented gray matter allows an individual to recall information more quickly, and to make connections among previous experiences that better prepare her for new situations. This process of myelination has been shown to peak at around age 50, which has something to do with why middle-aged people can make use of their life experiences so much better than young people (the other reason, of course, is the 50-somethings simply have more experience, period). It seems that, indeed, youth is somewhat wasted on the young.


  1. Oh, teens are wonderful, Massimo.

    The process and challenges of getting through the teen years is greatly underrated. I honestly wouldn't trade the process and the way they think for anything in the world. It really is fun and facsinating to watch.

    I enjoy them even when they're kind of misbehaving. :) So I'm not a very good disciplinarian obviously. (not wishing for any of them to be extremely naughty, of course)

  2. Teenagers?
    As a former middle school and high school teacher, I lasted two years, they just drove me crazy! I deeply respect those people that have the patience to educate them. Fortunately, I have about ten years to prepare to deal with my own teenager.

  3. Sheldon,

    Sure, they'll challenge you. But when it's your own, I think you'll often find yourself terribly proud of them for learning how to think (somewhat) by themselves. In terms of thinking for one self, I don't in any way encourage disrespect towards teachers or law enforcement. I tell them that their college teachers (in the case of our son) have worked really hard to get where they are, and if the must disagree or do something differently than they are asked to do, they must do so with utmost attitude of kindness and respect for the teacher. And I think it seems to work out alright so far. Our son says he likes college and most of his teachers. :)

    Influence from friends really is a big deal. I probably don't even need to tell you that. But I have encouraged and challenged my kids in return to spend less time with certain friends who have particularly bad habits. (a girl-friend of my teen girls is having a baby TODAY) So as tempting as it may be sometimes, I would not try to suggest that they spend zero time with troubled friends. They will encounter people through their whole life who get involved with unhealthy things, and it is far better for them to deal with the ups and downs of all that entails while they are still at home.

    Intentionally stay in touch with your child as he grows up, 7, 8, 10, 12 yrs old and beyond (even if he doesn't always act very enthusiastic about it). Ask him questions that will make him question why he is interested in certain friends, where he's going, who's there, and what they're all doing when the get there. If you don’t like what you hear, don’t be afraid to say “no”. If you fully intend to pay attention on consistent basis through these interesting times, I can assure you, that you will LOVE the person he grows up to be! :)

    best of luck to you with your little boy,

  4. Anonymous Cal,

    Thanks for the advice Cal. I certainly do think I will love the person my son comes to be, even through the frustrating teen years.

    Reflecting on some points in Massimo's post, and my experience as a teacher.


    I could see this happening on a daily basis. I recall this one boy, a really nice kid, who never really meant me any irritation. I would politely ask the class for some quiet attention while I explained the hour's activities. This kid simply could not give me one single minute of quiet attention! And now when I think about it, I think he reall did try to do so. He would often come to me after class and apologize for his disruption.

    Even beyond this one particular boy, imploring these kids to stay on task was a constant battle.

    Overall though, I really did genuinely like and enjoy the kids I taught.

    However, there were some kids that were just plain obnoxious and made it their mission to irritate the hell out of me.
    They did, I quit, and went on to my original profession. All for the better of everyone :)

  5. You always love them, but sometimes it stretches ones mental resources to like them! mine are 36 and 33 and still manage to drive me to distraction.

  6. What I still don't get though is that "teenagers" were, for the majority of our evolution, "adults."

    Consider, that life expectancies were pretty short for most of the time that we've been around 20-30 some odd years for the most part. Only "recently" have we managed to make it into the 50s with any consistency and only more recently, still longer.

    Teenager is a relatviely recent concept, really only coming into existence at the end of `19th Century, and then being expanded on in the US in the early part of the 20th, mainly in response first to the needs of the Great Depression and then, later, to the boon of the Post War Era.

    I bring all of this up because I have some mental conflict with the idea that teenagers are "less adult" than adults. Given human evolution, we couldn't have been effectively "immature" for all that time, could we?

    When we say today that teenagers are immature or their brains are still developing, how does that square with the fact that they were effectively "adults" for most of human history?

    Please note, I've been a thearapist and a social worker with children and teens for many, many years. Teenagers collectively drive me bat-shit crazy -- doing dumb things one moment and brilliant stuff the next. I'm rather puzzled at how we could survive for so long when the leaders of our time effectively had trouble remembering to take out the trash....

  7. Jody,

    I believe that for much of our evolutionary past there actually has been a block of years where certain individuals were considered "teens" or "not-quite-adults."

    Looking at modern hunter-gatherer populations as a reflection of our own past, we can observe a period where girls are sexually mature and physiologically capable of playing an adult role, but remain in an "inbetween" stage. During this time, they forage with their mothers or care for siblings/ other children in the village. The function is to teach the girl about childcare and how to sustain her family.

    I can imagine this being the case especially in early hominid populations where the environment was particularly dangerous (predators, poisonous plants, etc). In order to get your genes into the next generation, you better have a healthy child, and for that you'll need to learn how to care for for your kids.


