As many as 20 million Americans may have Attention Deficit Disorder. In the five years since Thom Hartmann first published his pioneering book, "Attention Deficit Disorder: A Different Perception," new findings support his theory linking ADD to the genetic makeup of men and women who hunted for their food in prehistoric times. Now, Hartmann has revised his groundbreaking book to include the latest research along with surprising information on studies that link second-hand smoke to disruptive behavior. This edition has a new introduction by famed Harvard psychiatrist Edward M. Hallowell, MD, co-author of the best-selling "Driven to Distraction.: