Erikson's stages of psychosocial development, as articulated by Erik Erikson, in collaboration with Joan Erikson, is a comprehensive psychoanalytic theory that identifies a series of eight stages, in which a healthy developing individual should pass through from infancy to late adulthood. All stages are present at birth but only begin to unfold according to both a natural scheme and one's ecological and cultural upbringing. In each stage, the person confronts, and hopefully masters, new challenges. Each stage builds upon the successful completion of earlier stages. The challenges of stages not successfully completed may be expected to reappear as problems in the future.