Only in the relatively recent past have scientists really begun studying the adolescent brain and the findings have been really enlightening. The adolescent period begins around age 11 or 12 and ends around age 25 or 26. In the beginning of adolescence the brain is only 80% developed and you can see in the image above where the brain is stands during adolescence. As in so many other developmental milestones there is a range of maturity, but what we see above can and should be expected in all adolescents. Understanding this is the first defense in supporting our youth during this time period; we don't expect a 6 month old to walk because we know he or she is not mature enough to, we now also know that adolescents lack the capacity to do certain things we expect of them as well.