Developmental psychology is the scientific study of how and why human beings change over the course of their life. Originally concerned with infants and children, the field has expanded to include adolescence, adult development, aging, and the entire lifespan. Developmental psychologists aim to explain how thinking, feeling, and behaviors change throughout life. This field examines change across three major dimensions: physical development, cognitive development, and socioemotional development.
John B. Watson and Jean-Jacques Rousseau are typically cited as providing the foundations for modern developmental psychology.
It generally focuses on how and why certain modifications throughout an individual’s life-cycle (cognitive, social, intellectual, personality) and human growth change over time. There are many theorists that have made a profound contribution to this area of psychology. For example, Erik Erikson developed a model of eight stages of psychological development. He believed that humans developed in stages throughout their lifetimes and this would affect their behaviors.
Psychosexual development, theories of cognitive development, stages of moral development, and stages of psychosocial development are a few categories of "Developmental psychology".