Adolescent behavioral problems, fast-changing moods, poor decision making, unhappiness, and rebellion have been blamed on “raging hormones” that accompany the physical transition to adulthood. But recent research now finds that these adolescent behaviors are the product of two factors: a flood of hormones and also a lack of the cognitive controls needed for mature behavior. By using high-powered magnetic resonance imaging (MRI) to map brain activity, scientists have discovered that the brain continues to develop (not in size, but in specialized regions) much longer than was previously thought. The best estimate at this time for when the brain is truly mature is 25 years of age. Thus, some youthful behaviors that were thought to be just hormone related (sensation seeking, poor decision making, lack of responsible behavior, and so on) now appear more related to the failure of certain parts of the brain to reach full adult development.