Developmental psychology, also known as Human Development, is the scientific study of progressive psychological changes that occur in human beings as they age. Originally concerned with infants and children, and later other periods of great change such as adolescence and aging, it now encompasses the entire life span. This field examines change across a broad range of topics including motor skills and other psycho-physiological processes, problem solving abilities, conceptual understanding, acquisition of language, moral understanding, and identity formation.

Developmental psychologists investigate key questions, such as whether children are qualitatively different from adults or simply lack the experience that adults draw upon. Other issues that they deal with is the question of whether development occurs through the gradual accumulation of knowledge or through shifts from one stage of thinking to another; or if children are born with innate knowledge or figure things out through experience; and whether development is driven by the social context or by something inside each child.

Developmental psychology informs several applied fields, including: educational psychology, child psychopathology and developmental forensics. Developmental psychology complements several other basic research fields in psychology including social psychology, cognitive psychology, cognitive development, and comparative psychology.

Many theoretical perspectives attempt to explain development, among the most prominent are: Jean Piaget's Stage Theory, Lev Vygotsky's Social Contextualism (and its heir, the Ecological Systems Theory of Urie Bronfenbrenner), and especially the information processing framework employed by cognitive psychology.

Developmental psychology is concerned not only with describing the characteristics of psychological change over time, but also seeks to explain the principles and internal workings underlying these changes. Understanding these factors is aided by the use of models. Developmental models are often computational, but they do not necessarily need to be. A model must simply account for the means by which a process takes place. This is sometimes done in reference to changes in the brain that may correspond to changes in behavior over the course of the development. Computational accounts of development often use either symbolic, connectionist (neural network), or dynamical systems models to explain the mechanisms of development.

Source : http://en.wikipedia.org