At a child care center, 18-month-old Hannah is clinging to her mother and crying as they enter. Her mother pulls Hannah’s hands from her arm, saying, “Don’t be such a crybaby and go play.” In a pediatrician’s waiting room, two-year-old Carlos climbs dangerously high on the furniture. He throws a toy at his mother when she calls his name. His mother laughs nervously and says quietly, “I don’t kn...