RE: Younger subs vs. older subs:Who has the edge?

Developmental psychology is the study of changes in behaviour during a lifetime. Many developmental psychologists study only a part of the lifespan. Most are chiefly interested in childhood and adolescence, the period of a person's life between birth and the early 20's.

There are four main theories of child development that psychologists use in research on the behaviour of children: (1) maturational theory, (2) psychoanalytical theory, (3) learning theory, and (4) cognitive theory.

Maturational theory states that the chief principle of developmental change is maturation, which means physiological "ripening," especially of the nervous system. Arnold L. Gesell, the leading American supporter of this theory, found that the growing child's behaviour seems to follow a set developmental pattern. He described in detail the ways in which behaviour changes with age. Gesell believed that differences among people result more from heredity than from environment.

Psychoanalytical theory is based on Sigmund Freud's theory of psychoanalysis. According to Freud, children are driven by impulses of sex and aggression. Children develop through a complicated interaction between their needs, based on sexual impulses, and the demands of their environment. Environmental demands are represented first by loving and restricting parents, and later by the children's own version of their parents' demands.

Anna Freud, Erik Erikson, and others have modified Freud's theory and applied it to child behaviour. In the psychoanalytical view of development, children change through conflict, chiefly between their own impulses and the demands of reality. A successful solution of this conflict brings normal development, and an unsuccessful solution may lead to mental illness.

Learning theory says a child's development depends mainly on experience with reward and punishment. The child must learn certain responses--such as speech, manners, and attitudes--to adults. Children learn these responses through their association with reinforcement (any condition that makes learning occur). If a mother smiles at her child each time the child is polite to adults, her smile reinforces the learning of manners. The task of the adult is to arrange the environment so that it provides suitable and effective reinforcements for desired behaviour.

Learning theorists base their ideas on two basic learning experiments--studies of classical conditioning by Ivan P. Pavlov and studies of instrumental conditioning by E. L. Thorndike and B. F. Skinner. Maturation and heredity have relatively little importance in the learning theory of development.

Cognitive theory regards the child as an active solver of problems. Cognitive theorists emphasize the role of a child's natural motivation as the key factor in development. This motivation can include the desire of children to satisfy their curiosity, master challenging tasks, or reduce the inconsistencies and ambiguities they find in the world about them. According to cognitive theory, children form their own theories about the world and the relationships among its different aspects. The theories are primitive at first, but become more realistic after they have been tested against the child's experience.

Comprehensive cognitive theories of development have been proposed by a number of authorities, including the Swiss psychologist Jean Piaget. Piaget described in detail how growing children change their ideas about number, cause, time, space, and morality. First, the children represent the world in terms of their own activities. Then they move to a limited set of generalizations based on their knowledge of specific cases. Finally, the children gain the ability to make valid and abstract generalizations about reality.

Maturity and old age.