Infancy is the developmental period that extends from birth to eighteen to twenty-four months. Infancy is a time of extreme dependence on adults. Many psychological activities are just beginning- language, symbolic thought, sensorimotor coordination, and social learning, for example. First grade typically marks the end of this period. Children master the fundamental skills of reading, writing, and arithmetic, and they are formally exposed to the larger world and its culture.
Achievement becomes a more central theme of the child s world, and self-control increases.
Adolescence is the developmental period of transition from childhood to early adulthood, entered approximately at ten to twelve years of age and ending between eighteen and twenty years of age. At this point in development, the pursuit of independence and an identity are prominent. Thought is more logical, abstract, and idealistic. More and more time is spent outside of the family during this period. Today, develpmentalists do not believe that change ends with adolescence.