Strictly speaking, the field of psychology
concerned with the lifelong process of change. "Change" here means any
qualitative and/or quantitative modification in structure and function: crawling
to walking, babbling to speaking, illogical reasoning to logical, infancy to
adolescence to maturity to old age, birth to death. When first articulated as a
substantive subdiscipline in psychology by G.S. Hall around the turn of the
century, it was quite explicitly this kind of "cradle-to-grave" field of
investigation. However, it should be noted that most of the scientists who call
themselves developmental psychologists are interested in childhood, indeed so
much so that for many the term developmental psychology has become equivalent to
child psychology.