Behavior: Why Junior Won't Sit Still

For a disorder that is as widespread and as closely studied as hyperactivity, scientists know precious little about it. Lots of children -- and many adults, for that matter -- have trouble paying attention and keeping still. But without a clear understanding of what causes the syndrome now known as attention deficit-hyperactivity disorder, parents and teachers have no surefire way of distinguishing true hyperactivity from other learning disabilities, an abused-child situation or just plain bratty behavior. Doctors have long suspected there was a real physiological problem lurking behind the psychosocial maladjustment, but in more than 20 years of intense scientific scrutiny,...