The conventional view of brain development has been that most of this takes place in utero and in the first three years, with the further development continuing until the brain is fully mature at around 10-12 years of age. The turbulence of adolescent behavior has been deemed to be mostly caused by hormonal changes. Piaget, who identified four stages of cognitive development, assessed that his highest stage — that of formal, abstract reasoning — occurred around 13-14 years (although not everyone reaches this level, which requires appropriate education).
Recent studies, however, are painting a different picture. Evidence is converging that the brain continues to grow and develop throughout the teen years, and possibly even into the early twenties. Indeed, early adolescence appears to be a time of significant growth and development.
The vulnerability of the adolescent brain to drugs and alcohol is well-established. The picture that is now emerging is that adolescence is a time of heightened vulnerability partly because different systems are maturing according to different timetables — adolescence is a time when brain systems are out-of-sync, as it were. Adolescence is increasingly seen as a critical period for a reorganization of regulatory systems. This reorganization is both hazardous and an opportunity.
Adolescence, then, is rightly seen as a time when we take our first steps on the path we will take through adulthood. But this cliché has a deeper meaning than we ever suspected. For one thing, an important part of brain development during adolescence concerns the pruning of unused neurons and connections, resulting in a strengthening of those connections that are most used. In other words, it’s a time to lose the things we don’t care about, and strengthen those we do.
Much of this process seems to occur in the frontal cortex, where our “higher” faculties, such as decision-making, goal-setting, and executive control, reside. Maturation of the brain seems to occur roughly from the back to the front: the cerebellum (involved in motor skills) is the first to mature, and the prefrontal cortex the last (possibly not until the mid-twenties).
Poor decision-making, reckless behavior, rule breaking, the tendency toward emotional outbursts, fewer organizational abilities, and lack of ability to process abstract concepts have all been associated with problems in pruning. The ability to multi-task continues to develop until ages 16-17. The delay in maturation of the prefrontal cortex has also been implicated in difficulties in reading emotional cues, which in turn has implications for teens’ ability to communicate with others.
In other words, we as adults may often expect too much from teenagers. We need to keep these cognitive limitations in mind, particularly when teens are confronting with demanding situations. Truly it has been said, the teenage brain is a work in progress, not a finished product.