Developmental psychology is the study of changes in behavior during a lifetime. Many developmental psychologists study only a part of the life span. Most of these psychologists are chiefly interested in childhood and adolescence, the period between birth, and the early twenties. There are four main theories of child development that psychologists use in research on the behavior of children. The theories are; maturational theory, psychoanalytic theory, learning theory, and cognitive theory.
             The maturational theory states the principles of developmental change is maturation, which means ripening of the nervous system.
             The psychoanalytic theory is based on a theory by Sigmund Freud. According to Freud, children are driven by impulse of sex and aggression. Children develop through an interaction between their needs, which are based on sexual impulse, and also the demands of their environment.
             The learning theory says that a child's development depends on experiences of rewards and punishments. The child has to learn certain responses like; speech, and attitudes from adults. Children can learn these responses by association of reinforcement. The focus of the parents is to arrange the environment so that it provides suitable reinforcements for learning. Maturation and heredity have no importance in this theory.
             The cognitive theory regards the child as a problem solver. Cognitive theorists emphasize the role of a child's natural motivation as a key factor in development. This motivation includes the desire of children to satisfy curiosity, master tasks, reduce imperfections, and ambiguities that may in the world around.
             Children form their own theories about the world and relationships. The theories are primitive at first, but later become realistic after the child has and a chance to experience it.
             Erik Erikson was an American psychoanalyst. He became best known for his ideas on how human beings develop a sense...