Every parent dreads it.
Almost overnight a sweet, cheerful, obedient child mutates into a churlish monster prone to recklessness and unpredictable mood swings. This is adolescence. Parents and experts have always blamed the same hormones that catapult young bodies into adulthood for the sleeping until noon, the reckless driving, the drug use and the other woes of adolescence. But recent research shows that what's going on above teen-agers' necks, not raging hormones, explains the changes. Beginning around age 11, the brain undergoes major reorganization in an area associated with things like social behavior and impulse control.