Erik Erikson was a German-American developmental psychologist known for his theory of psychosocial development. The theory describes 8 stages of human development across the lifespan. Each stage presents a psychosocial crisis that must be resolved through how one relates to others. Successful resolution leads to a healthy personality and the acquisition of basic virtues or strengths. Erikson made important contributions in applying psychoanalytic ideas to social and cultural influences on development.