Psychosocial development is a comprehensive psychological theory first proposed by German-American psychologist Erik Erikson, a student of Sigmund Freud, after observing Native American tribes of the Plains and the Pacific Coast. The theory suggests that individual identity (or ego) evolves throughout life in balance with broad sociocultural pressures. This idea is in contrast to Freud, who believed that identity was shaped through psychological forces experienced largely before the age of twenty.