Development

Development is defined as organized and sequential intraindividual change, from conception to the end of life, of an organism’s behavior and of the systems and processes that underlie behavior. Life-span development encompasses several categories of organized and sequential change including ontogenesis (development of the individual across the life span), orthogenesis (normal development), embryogenesis (development of the embryo), pathogenesis (development of psychopathology), and microgenesis (development on a very small time scale, such as development of a single percept). But life-span development is also comparative and, thus, includes phylogenesis (evolution—development of the species) as well as historical and cultural development.

Human ontogenesis/orthogenesis is the broadest of the developmental categories, and within this category there are a number of age-related areas of study—infancy, toddlerhood, childhood, adolescence, early adult, mature ...