Venerable pediatrician Brazelton (Touchpoints) teams up with child psychologist Joshua D. Sparrow to adapt his theory of "touchpoints" to children ages three to six. In his earlier work, Brazelton explained that infants undergo periods of behavioral regression (touchpoints) before each developmental burst. Here he addresses issues like sibling rivalry, bedwetting, tantrums and lying as normal aspects of development, and suggests ways parents can be emotionally supportive. The first of the book's two major sections follows four imaginary children with varying, composite temperaments (an active boy, a quiet boy, an intense girl and a cheerful girl), exploring everything from adjusting to a new sibling to making friends. Readers may soon find themselves skipping all but the portions directly related to their own child's temperament type (and weeding out the fictional scenes to get to the nitty-gritty of what to do when a child lies, wets the bed, etc.). In the second section, the authors straightforwardly discuss various contemporary parenting concerns, such as the pros and cons of computers and dealing with divorce. Throughout, Brazelton and Sparrow maintain a characteristically comforting tone, reminding parents that it's best to accept a child's temperament while helping her adapt to the world. The authors not only point toward the predictable touchpoints for this age group but note that parents, too, may react to transition in certain ways, such as worrying that one is abandoning their first child when a new baby arrives. As always, Brazelton's poised, encouraging voice guides parents through the developmental maze. Photos. (Sept.)