Ambassador to the Teen Brain

As one moves through the teen years, the judgment of peers becomes a deep preoccupation. Hazardous behaviors grow more attractive. And in many cases, ills that plague us as adults—mood problems, eating disorders, drug abuse—first strike. But there's more to adolescence than angst and excess. In her new book, Inventing Ourselves, neuroscientist Sarah-Jayne Blakemore of University College London reveals how brains morph and new faculties are flexed during this tumultuous period of self-formation.

Teen brains are hypersensitive to signs of social reward and rejection, experiments suggest. How does this make sense developmentally?

The whole point of this period of life is to become an independent adult. You need to grow more and more independent from your family and at the same time establish yourself as part of your peer group and work out where you lie in complicated social hierarchies. There's a big incentive to be accepted by your peers. This increase in the importance of the social environment can help explain many of the experimental results.

Most teens are still developing self-control. What are some other capacities in the works?

Many executive functions, such as the ability to inhibit inappropriate responses. Or to plan what you're going to do today or next week or next year. That develops quite steeply, as does introspection, the ability to be aware of your behavior and thought processes. All rely on the prefrontal cortex, which, like many brain regions, is undergoing massive development during adolescence and into the 20s.

Many people have a negative view of the teen years, including their own. does the science challenge that?

The adolescent brain is very plastic; it's amenable to learning and acquiring new information. Some studies show that adolescents are particularly creative compared to other age groups. The teen years can be hard, but teenagers are also very full of passion, creativity, and novel thought.

How do teens' responsiveness to reward—and relative slowness to learn from punishment—affect their interactions with adults?

Parenting is often largely about punishment: If you don't do this, then you can't have your pocket money or your time on the iPad. And it's hard to reframe that in terms of reward. It doesn't come naturally, I think, to most parents. In fact, there's quite good evidence that immediate rewards—not rewards promised at some point in the future—have a bigger impact than punishment on adolescent behavior. It's one example of how, generally, it is not ideal to assume that your teenager has the same mindset that you do.