A new born baby has to be dependent on the environment around him. But as the time passes, he begins to sit, then to stand, then to walk and to run at last. At first, he just weeps but with the passage of time, smile begins to appear on his face. Then he expresses anger, love and hatred. At first, he cannot speak. Gradually, he begins to speak word and then utters broken sentences. Afterward, a time comes and he speaks the mother tongue fluently. At birth, his society is just confined to his parents, brothers and sisters. Gradually,
his contacts become larger and deeper. They expand from street to city. All these changes bring the child to the stage of maturity. In psychology, these changes are considered as ‘development’.
Development is a continual process beginning in the conception and ending with death. Although physical changes may be the most obvious, we also change socially, personally, cognitively, intellectually and educationally. The subject of human development has traditionally been the primary concern of educational psychologists. Most commonly the field is called developmental psychology. It focuses primarily on child development. Psychology itself is often defined as the scientific study of behavior and mental process. Development deals with how individuals change with time while remaining in some respects the same. In the present days, the field of life-span development has been multidisciplinary. It encompasses not only psychology but also biology, sociology and anthropology. A developmental psychologist should avoid the tendency to view the various academic disciplines as somehow separated into water tight departments. The academic disciplines are loosely defined. The borderlines are so, vague that a researcher gives little thought to whether he is invading discipline’s field of study. Such academic overlap encourages a freshness of approach and functions as a stimulus in advancing the frontiers of knowledge. A true researcher welcomes aid and collaboration from any qualified person where or not that person belongs to the same academic discipline.