Erik Erikson developed an 8 stage theory of psychosocial development where individuals face conflicts or crises at each stage that shape personality. The stages span from infancy to late adulthood and involve developing trust, autonomy, initiative, industry, identity, intimacy, generativity, and integrity. Successful resolution of the conflicts leads to healthy development while failure can result in feelings of inadequacy. Criticisms include its focus on male development and difficulty measuring some concepts.