Sarah-Jayne Blakemore: The mysterious workings of the adolescent brain


Translator: Joseph Geni
Reviewer: Morton Bast Fifteen years ago, it was widely assumed that the vast majority of brain development takes place in the first few years of life. Back then, 15 years ago, we didn’t have the ability to look inside the living human brain and track development across the lifespan. In the past decade or so, mainly due to advances in brain imaging technology such as magnetic resonance imaging, or MRI, neuroscientists have started to look inside the living human brain of all ages, and to track changes in brain structure and brain function, so we use structural MRI if you’d like to take a snapshot, a photograph, at really high resolution of the inside of the living human brain, and we can ask questions like, how much gray matter does the brain contain, and how does that change with age? And we also use functional MRI, called fMRI, to take a video, a movie, of brain activity when participants are taking part in some kind of task like thinking or feeling or perceiving something. So many labs around the world are involved in this kind of research, and we now have a really rich and detailed picture of how the living human brain develops, and this picture has radically changed the way we think about human brain development by revealing that it’s not all over in early childhood, and instead, the brain continues to develop right throughout adolescence and into the ’20s and ’30s. So adolescence is defined as the period of life that starts with the biological, hormonal, physical changes of puberty and ends at the age at which an individual attains a stable, independent role in society. (Laughter) It can go on a long time. (Laughter) One of the brain regions that changes most dramatically during adolescence is called prefrontal cortex. So this is a model of the human brain, and this is prefrontal cortex, right at the front. Prefrontal cortex is an interesting brain area. It’s proportionally much bigger in humans than in any other species, and it’s involved in a whole range of high level cognitive functions, things like decision-making, planning, planning what you’re going to do tomorrow or next week or next year, inhibiting inappropriate behavior, so stopping yourself saying something really rude or doing something really stupid. It’s also involved in social interaction, understanding other people, and self-awareness. So MRI studies looking at the development of this region have shown that it really undergoes dramatic development during the period of adolescence. So if you look at gray matter volume, for example, gray matter volume across age from age four to 22 years increases during childhood, which is what you can see on this graph. It peaks in early adolescence. The arrows indicate peak gray matter volume in prefrontal cortex. You can see that that peak happens a couple of years later in boys relative to girls, and that’s probably because boys go through puberty a couple of years later than girls on average, and then during adolescence, there’s a significant decline in gray matter volume in prefrontal cortex. Now that might sound bad, but actually this is a really important developmental process, because gray matter contains cell bodies and connections between cells, the synapses, and this decline in gray matter volume during prefrontal cortex is thought to correspond to synaptic pruning, the elimination of unwanted synapses. This is a really important process. It’s partly dependent on the environment that the animal or the human is in, and the synapses that are being used are strengthened, and synapses that aren’t being used in that particular environment are pruned away. You can think of it a bit like pruning a rosebush. You prune away the weaker branches so that the remaining, important branches, can grow stronger, and this process, which effectively fine-tunes brain tissue according to the species-specific environment, is happening in prefrontal cortex and in other brain regions during the period of human adolescence. So a second line of inquiry that we use to track changes in the adolescent brain is using functional MRI to look at changes in brain activity across age. So I’ll just give you an example from my lab. So in my lab, we’re interested in the social brain, that is the network of brain regions that we use to understand other people and to interact with other people. So I like to show a photograph of a soccer game to illustrate two aspects of how your social brains work. So this is a soccer game. (Laughter) Michael Owen has just missed a goal, and he’s lying on the ground, and the first aspect of the social brain that this picture really nicely illustrates is how automatic and instinctive social emotional responses are, so within a split second of Michael Owen missing this goal, everyone is doing the same thing with their arms and the same thing with their face, even Michael Owen as he slides along the grass, is doing the same thing with his arms, and presumably has a similar facial expression, and the only people who don’t are the guys in yellow at the back — (Laughs) — and I think they’re on the wrong end of the stadium, and they’re doing another social emotional response that we all instantly recognize, and that’s the second aspect of the social brain that this picture really nicely illustrates, how good we are at reading other people’s behavior, their actions, their gestures, their facial expressions, in terms of their underlying emotions and mental states. So you don’t have to ask any of these guys. You have a pretty good idea of what they’re feeling and thinking at this precise moment in time. So that’s what we’re interested in looking at in my lab. So in my lab, we bring adolescents and adults into the lab to have a brain scan, we give them some kind of task that involves thinking about other people, their minds, their mental states, their emotions, and one of the findings that we’ve found several times now, as have other labs around the world, is part of the prefrontal cortex called medial prefrontal cortex, which is shown in blue on the slide, and it’s right in the middle of prefrontal cortex in the midline of your head. This region is more active in adolescents when they make these social decisions and think about other people than it is in adults, and this is actually a meta-analysis of nine different studies in this area from labs around the world, and they all show the same thing, that activity in this medial prefrontal cortex area decreases during the period of adolescence. And we think that might be because adolescents and adults use a different mental approach, a different cognitive strategy, to make social decisions, and one way of looking at that is to do behavioral studies whereby we bring people into the lab and we give them some kind of behavioral task, and I’ll just give you another example of the kind of task that we use in my lab. So imagine that you’re the participant in one of our experiments. You come into the lab, you see this computerized task. In this task, you see a set of shelves. Now, there are objects on these shelves, on some of them, and you’ll notice there’s a guy standing behind the set of shelves, and there are some objects that he can’t see. They’re occluded, from his point of view, with a kind of gray piece of wood. This is the same set of shelves from his point of view. Notice that there are only some objects that he can see, whereas there are many more objects that you can see. Now your task is to move objects around. The director, standing behind the set of shelves, is going to direct you to move objects around, but remember, he’s not going to ask you to move objects that he can’t see. This introduces a really interesting condition whereby there’s a kind of conflict between your perspective and the director’s perspective. So imagine he tells you to move the top truck left. There are three trucks there. You’re going to instinctively go for the white truck, because that’s the top truck from your perspective, but then you have to remember, “Oh, he can’t see that truck, so he must mean me to move the blue truck,” which is the top truck from his perspective. Now believe it or not, normal, healthy, intelligent adults like you make errors about 50 percent of the time on that kind of trial. They move the white truck instead of the blue truck. So we give this kind of task to adolescents and adults, and we also have a control condition where there’s no director and instead we give people a rule. We tell them, okay, we’re going to do exactly the same thing but this time there’s no director. Instead you’ve got to ignore objects with the dark gray background. You’ll see that this is exactly the same condition, only in the no-director condition they just have to remember to apply this somewhat arbitrary rule, whereas in the director condition, they have to remember to take into account the director’s perspective in order to guide their ongoing behavior. Okay, so if I just show you the percentage errors in a large developmental study we did, this is in a study ranging from age seven to adulthood, and what you’re going to see is the percentage errors in the adult group in both conditions, so the gray is the director condition, and you see that our intelligent adults are making errors about 50 percent of the time, whereas they make far fewer errors when there’s no director present, when they just have to remember that rule of ignoring the gray background. Developmentally, these two conditions develop in exactly the same way. Between late childhood and mid-adolescence, there’s an improvement, in other words a reduction of errors, in both of these trials, in both of these conditions. But it’s when you compare the last two groups, the mid-adolescent group and the adult group where things get really interesting, because there, there is no continued improvement in the no-director condition. In other words, everything you need to do in order to remember the rule and apply it seems to be fully developed by mid-adolescence, whereas in contrast, if you look at the last two gray bars, there’s still a significant improvement in the director condition between mid-adolescence and adulthood, and what this means is that the ability to take into account someone else’s perspective in order to guide ongoing behavior, which is something, by the way, that we do in everyday life all the time, is still developing in mid-to-late adolescence. So if you have a teenage son or a daughter and you sometimes think they have problems taking other people’s perspectives, you’re right. They do. And this is why. So we sometimes laugh about teenagers. They’re parodied, sometimes even demonized in the media for their kind of typical teenage behavior. They take risks, they’re sometimes moody, they’re very self-conscious. I have a really nice anecdote from a friend of mine who said that the thing he noticed most about his teenage daughters before and after puberty was their level of embarrassment in front of him. So, he said, “Before puberty, if my two daughters were messing around in a shop, I’d say, ‘Hey, stop messing around and I’ll sing your favorite song,’ and instantly they’d stop messing around and he’d sing their favorite song. After puberty, that became the threat. (Laughter) The very notion of their dad singing in public was enough to make them behave. So people often ask, “Well, is adolescence a kind of recent phenomenon? Is it something we’ve invented recently in the West?” And actually, the answer is probably not. There are lots of descriptions of adolescence in history that sound very similar to the descriptions we use today. So there’s a famous quote by Shakespeare from “The Winter’s Tale” where he describes adolescence as follows: “I would there were no age between ten and three-and-twenty, or that youth would sleep out the rest; for there is nothing in the between but getting wenches with child, wronging the ancientry, stealing, fighting.” (Laughter) He then goes on to say, “Having said that, would any but these boiled brains of nineteen and two-and-twenty hunt in this weather?” (Laughter) So almost 400 years ago, Shakespeare was portraying adolescents in a very similar light to the light that we portray them in today, but today we try to understand their behavior in terms of the underlying changes that are going on in their brain. So for example, take risk-taking. We know that adolescents have a tendency to take risks. They do. They take more risks than children or adults, and they are particularly prone to taking risks when they’re with their friends. There’s an important drive to become independent from one’s parents and to impress one’s friends in adolescence. But now we try to understand that in terms of the development of a part of their brain called the limbic system, so I’m going to show you the limbic system in red in the slide behind me, and also on this brain. So the limbic system is right deep inside the brain, and it’s involved in things like emotion processing and reward processing. It gives you the rewarding feeling out of doing fun things, including taking risks. It gives you the kick out of taking risks. And this region, the regions within the limbic system, have been found to be hypersensitive to the rewarding feeling of risk-taking in adolescents compared with adults, and at the very same time, the prefrontal cortex, which you can see in blue in the slide here, which stops us taking excessive risks, is still very much in development in adolescents. So brain research has shown that the adolescent brain undergoes really quite profound development, and this has implications for education, for rehabilitation, and intervention. The environment, including teaching, can and does shape the developing adolescent brain, and yet it’s only relatively recently that we have been routinely educating teenagers in the West. All four of my grandparents, for example, left school in their early adolescence. They had no choice. And that’s still the case for many, many teenagers around the world today. Forty percent of teenagers don’t have access to secondary school education. And yet, this is a period of life where the brain is particularly adaptable and malleable. It’s a fantastic opportunity for learning and creativity. So what’s sometimes seen as the problem with adolescents — heightened risk-taking, poor impulse control, self-consciousness — shouldn’t be stigmatized. It actually reflects changes in the brain that provide an excellent opportunity for education and social development. Thank you. (Applause) (Applause)

100 thoughts on “Sarah-Jayne Blakemore: The mysterious workings of the adolescent brain

  1. What bullshit. "If you have a teenage son or daughter and you think that they have a problem taking in other peoples perspectives, you're right." Their study showed that 45% of adults have this problem compared to teenagers from 50-60%. I think the people in this study have trouble taking in other perspectives and results from the same study. Maybe they could have said that "if you have a teenage son or daughter then you have a problem taking in other peoples perspective, and so do they."

  2. I guess my pre frontal cortex isn't soo good, bad at planning, so inappropriate stuff, sometimes say very rude things, because I'm rather blunt…..no wait, I'm terrible at planning.

  3. ARRGGG HUMANS ARE ANIMALS!! fuck sake….sorry, I get pissed off when people say, animals and Humans. You can say, humans…do this, compared to other animals, but not humans…. compared to animals.

  4. translating from a German translation of the text: "Our youth is degenerate and undisciplined. The young people don't listen to their parents anymore. The end of the world is near"
    something along those lines

  5. Because they are not thought enough to know what they are doing is wrong or right because parents are to buys doing there own things.

  6. Hmmm… she ends with pointing out there is an "opportunity" during later adolescence for changing the social development of people… In today's police states, does that seem ominous to anyone else but me?

  7. If you look at other research, especially developmental psychology, it addresses this. According to the data, not every adult develops past the teen stage, so even though they are physically adult they remain mental and emotional teenagers.

  8. where!? how, show me? wtf? i am genuinely curious. i googled the damn concept and got some religious nut bag that scammed his way out of high school talking out of his ass. i cant find a single reliable source.

  9. Could be, it was a guess and I could have just insulted all of NK…..but I guess I have never been there so don't know. If lots of others agree with me, then I guess I may be right.

  10. This video explains the nature of a great many Youtube commenters. According to her definition, most people here don't seem to have left adolescence.

  11. I desperately want to disagree with you but I can't help but point out that I think that her private parts must taste like strawberries. You win.

  12. why is this video working normally on Google chrome but does not work on opera?? I find that few other videos on youtube also don't work on opera I don't know why, the player shows up for a second and then disappear and there's just black screen instead of player or vid :/

  13. She got it right. Soccer is not football….soccer, is soccer, played with a soccer ball, where football, is played with a…..drum roll……football….you britts can whine and complain but you can't change this fact, just the same as you can't change the fact That you britts all wear platform shoes to keep your knuckles from dragging the ground, and I know that's fact because I.googled it….

  14. I see your point. But I know of experiments similar to this where they control for these things (e.g. implying that the director hasn't seen the scene before). Also, there are experiments with different set-ups that actually show that adults are way more capable (results > the %50 here) of taking others' perspectives into account (even when not directly told to do so) than teenagers. Maybe she should have elaborated on the set-up a bit more or used other examples of such experiments.

  15. I was actually referred here by a Catholic website.

    Imagine, then, the devastation to the teenage brain if a child is sexually abused by a priest in the Catholic church, and the priest is hidden and protected by the church and its followers while the child is scorned, shunned or bullied. It is horrifying to see what the Catholic church has done in God's name.

  16. Fascinating. would like to show this to my teenage students but my guess is that they wouldnt be able to concentrate long enough to understand it!

  17. This video suits my research essay about the biological development of the adolescent brain and analysis of how the adolescent interpret communication obscurely when an adult speaks with one.

    (If anyone has a better thesis for my essay. Feel free to correct and adjust. It will benefit both of us. )):)

  18. My comment doesn't suggest that anyone is an idiot, nor that I lack respect. Just that it appears that a lot of comments on Youtube are made without due thought or consideration of consequences. What you say about respect is true, but you need to start by respecting yourself enough to not need to take comments personally and justify yourself.

  19. Psychologists are hyperobsessed with binary narratives… They're so primitive! But of course, they have to be to justify the quality of the academic work they do.

  20. Well that's kinda obvious. When you have kids etc. why would you be commenting on youtube. You'll be commenting on your kids 😉

  21. Sarah said 9 studies have shown increased MPFC activity in adolescents, then straight after says studies show decreased activity during the period of adolescence. Can anyone clarify which it is? Does she mean it peaks in adolescence then decreases towards adulthood?

  22. People who make statements as yours also have their own 'blind spots' in fundamental areas of social adeptness.

  23. In order to establish a healthy and enriching environment for the developing adolescent brain, perhaps the implementation of awareness-based classes or workshops may assist all those whom interact with adolescents. There are several approaches one can put into use with respect to such a natural occurrence of human behavior, however, the gradual development of a human being's social (and individual) connectivity takes time – maturation is a process which requires effort and constant attention. Thus, adolescents will continue to express their typical behavior but it can be in more moderate and tolerant ways. Simply, culture and its many systems (i.e. educational, athletic) may need to emphasize the importance of having adolescents (or even children, if possible) train their malleable brains to build a more intimate relationship with self-awareness, whether through meditation or other mindfulness-based exercises.

  24. I am so glad that she provided the Shakespeare quotes. Lately, I've been hearing more and more about the teenage/adolescent years being a recent/made up western concept. Though our society does seem to devalue what teenagers are capable of, there is now proof that some very specific developments are happening during that time in life. It's a real stage that requires unique guidance & attention. Excellent talk.

  25. I feel like it is easy to hate in the absence of information. This was an extremely educational talk for me and it helps me understand myself and others around me.

  26. School of life makes wise
    Yes, indeed, education can have a constructive influence on the youngster. But it's not that easy! Brains belong to individuals with their special speed of working and ripening. So differ 'lark-learning-types' from 'owl-learning-types', extraverted learners differ from introverted et cetera. And quite often the long schooling periods prevent the young from getting mature, because schools don't deliver the hard knocks insensitive persons need urgently. Role changing games are not new, and of course they are good training. When that bright girl talks about her grandparents, she seems not to be aware, that reduced schooling is a good thing to learn life. Would have Shakespeare become Shakespeare hanging out in schools and universities?

  27. It doesn't portray every adolescent whose different ways of living vary from one another, I wasn't a risk taker before but now as a young adult I am since I know the consequences before hand and to decide whether or not I follow through

  28. dont like how she talks..she talks too fast u can't even have the time to think about what she's talking about

  29. I think Teenagers are really good at seeking out new experiences, they seeking out risks and they recognizing social or being sensitive to social and emotional information.

  30. Can someone help me connect her ideas? Like how gray matter declines during adolescence, and how good people are at reading social expressions and interactions and then her behavioral studies. What do you think the main point that she is trying to get at with these?

  31. Scientist often talk about the brain in a biased context. Implying that the teenage mind controls the behavior of the person vs a teenage mind reflecting circumstances that the person is experiencing and adapting to it.

  32. We need to demolish every school (in the US) then restructure the entire system based on what will benefit our kids for the rest of their lives, not benefit the government for its statistics and its brainwashing program. Teach them who they are, what they’re passionate about and how to make things better for the world. Not that hard, right?

  33. Look up a girl named Alma Deutscher and see what a child's and an adolescent's brain can do. And it occurs to me that if a brain is exercised and used to its maximum potential early on, there might be a lot less 'pruning' going on as a later adolescent and a young adult.

  34. 1:50–1:55 so does this mean that teenagers could function as adult organism better? If they're given say a hypothetical situation, a family, a baby to take care of, a job that is stable and the basic education writing reading math they could in-fact behave better instead of impulsive? So everything the teens are doing their brain is just shaping itself into something immature then? Basically a correlation from peers and the environment which has been said multiple times?

    Sounds like to me if Grey matter is needed to mature people and it's synaptic pruning away the unnecessary parts what if it's pruning away the adult parts it's getting because you are in fact delaying true adolescence and adulthood. To me from the sound of it, something that makes someone so mature that goes down the toilet is a disadvantage than an advantage out in the wild. Animals leave their parents to prevent inbreeding then yes test their skills out as our teens are but it's done in a flash. Cows function as adults at 15 and die commonly at 35, humans before modern medicine died at these ages due to disease. So wouldn't the teens who lost their parents need to function as an adult?

    Really hard to understand what she's saying.

  35. Admittedly im 16 so i'm coming from that perspective but she's right about the way teenagers are viewed in the media. You literally see virtually nothing but mocking and invalidation from adults and yet are told to act like one. Sorry i'm moody and all but you acting like that i shouldn't be upset because i'm "just a hormonal teenager" doesn't help, debra.

  36. Why do some people want 16 year olds to vote and why does the military love 18 and 19 year olds? Exploitable underdeveloped brains. I bet all countries who restricted voting and military service to 25 years of age and up would look very different. We pay a price for being fair with regards to voting and public service in government.

  37. I'm almost 14 years old. I've only dealt with teenagers just like me being demonized for crap we can't physically or mentally control. Its refreshing to finally see someone understand how we feel and take the scientific side and acknowledge it's not really completely our fault we act this way.

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