Her quest to understand the teenage brain

Sarah-Jayne Blakemore’s TED talk on adolescent brain development has 2.4 million views and counting.
Sarah-Jayne Blakemore’s TED talk on adolescent brain development has 2.4 million views and counting.Handout

It’s more or less a parental rite of passage, that moment when you stand before an adolescent child whose confounding behavior has been so moody, risky, destructive, self-destructive, and/or just plain stupid that you are forced to ask yourself, “Who is this kid?”

Dr. Sarah-Jayne Blakemore, author of 2018’s “Inventing Ourselves: The Secret Life of the Teenage Brain,” has some very clear ideas that just might clear up a few questions and debunk some long-held beliefs. A professor of cognitive neuroscience at University College London, Blakemore is a leading expert on adolescent brain development, with multiple awards for her groundbreaking research and more than 100 published scientific papers to her credit. Her lively TED talk on the subject has 2.4 million views and counting.


Q. We tend to write off the unpredictable, impulsive, self-absorbed behavior of teens as the product of hormones, but are advanced brain scans now telling a different story?

A. Scans are part of the jigsaw puzzle. Until 20 years ago, we thought hormonal and social changes made kids difficult and rebellious. But now, we’re understanding adolescent brains are transitioning and reorganizing, making adaptive biological changes. They’re particularly malleable. We know from MRI scans that adolescent brains change in terms of structure and function, and composition changes are huge, with a steady increase in white matter into the 20s and 30s. Some synapses get pruned, all making the brain more efficient.

Q. You’ve noted that this period of brain development has commonalities not just across human cultures, but also across species and throughout history.

A. That’s right. All species go through a period of adolescence between puberty and sexual maturity. In rats, you can see an increase in risk taking and socialization, just like in humans. And you go back as far as Socrates and Aristotle and the way they describe the age group is the way we stereotypically describe teens today — lazy, disrespectful, impulsive. It’s not usually socially acceptable to be so publicly scathing, but teens get a bad rap.


Q. One of the major implications for these findings is better understanding mental illness in teens — what is it about late adolescence that makes some brains so vulnerable to schizophrenia, eating disorders, self-harm?

A. We don’t know yet, and I suspect when we do, it will be very complicated. We’re probably born with vulnerabilities, but why they kick in during adolescence? Maybe because all these changes happen at the same time — the hormonal and physical changes of puberty, going to different schools, social and peer pressures, increased self-awareness and awareness of the future, all the changes in the brain. All together, it makes this a period of real vulnerability.

Q. I love the title — “Inventing Ourselves,” because that fertile period between childhood and full adulthood is really about transformation as adolescents develop a sense of identity.

A. Adolescence is all about becoming an independent adult — the evolutionary drive to fit in with peers, establishing oneself in the social hierarchy. It’s a period where we place more importance in how others see us — fashion styles, musical tastes, what kind of people we hang out with. We begin to develop our moral and ethical beliefs and a profound sense of self and identity. It’s the first time all this takes a hugely increased level of importance.


Q. How should this information affect the way we interact with teens — as parents, as educators?

A. We should be a bit more understanding of all the turmoil. They’re not just being lazy or rebellious, but going through protracted biological changes. That understanding has helped me as a parent.

Q. What about implications for law and policy?

A. The legal implications are very interesting. Because the brain is still developing, teens are particularly susceptible to peer influence and often commit crimes with friends that they wouldn’t have on their own. But because the brain is changing, teens have increased capacity for atonement and rehabilitation than someone in middle age, and punishments should take that into account.

Q. This starts to get murky when you consider at what age we should consider adulthood.

A. That can’t be answered by brain imaging. There’s no magic age, and it’s different between individuals.

Q. What are the biggest takeaways you’d like people to remember?

A. Contrary to what we previously thought, there’s a huge amount of development going on in the brain that doesn’t stop in childhood, but continues right through adulthood. And this brain development is relevant to a lot of typical teen behavior — the risk taking, peer influence, moodiness — and it is why a lot of mental health problems normally appear in adolescence. It’s really useful to know this to understand teen behavior, like why they have trouble getting up in the morning. It’s not laziness. So we really need to stop demonizing, stereotyping, and being negative about adolescent behavior, because teens are undergoing very profound developmental changes — in their brains, body, behavior, and self-identity.


Karen Campbell can be reached at karencampbell4@rcn.com