A three-year-old is a real puzzle to parents, sometimes anxious to please and befriend, sometimes strong-willed and difficult to get along with. At the heart of the three-year-old's personality is often an emotional insecurity--and this causes a host of problems for parents Drs. Ames and Ilg, recognized authorities on child behavior and development, help parents understand what's going on inside that three-year-old head, what problems children have,...