Adolescence is considered a difficult time of life and one in which a number of changes occur as the individual achieves a certain integration of different aspects of personality. One approach to the cognitive and emotional transitions made at different times of life is to consider how the changes in, say, adolescence are linked to a continuum of change beginning in childhood and continuing throughout life. Some theorists, such as Piaget, were interested primarily in the transitions of childhood and youth, while others, such as Erikson, saw all of life as a series of transitions and offered a continuum of stages covering all of life. Piaget became fascinated in his early studies with his discovery that children of the same age often gave the same incorrect answers to questions, suggesting that there were consistent, qualitative differences in the nature of reasoning at different ages, not simply a quantitative increase in the amount of intelligence or knowledge. This discovery marked the beginning of Piaget's continuing effort to identify changes in the way children think, and how they perceive their world in different ways at different points in development. Piaget's contributions can be summarized by grouping them into four main areas. First, he produced literature on the general stages of intellectual development from infancy through adulthood. This concern occupied him from 1925 to 1940, and after 1940 he began to describe some of the developmental stages in formal, structural terms using models from symbolic logic. The different stages postulated by Piaget help to explain different rats of learning at different ages as well as the types of learning possible at different ages for the majority of the population. Learning itself is seen by Piaget as a process of discovery on the part of the individual, and learning as a formal activity becomes a system of organization by which instruction is enhanced by the way the teacher arranges...
