Psychologists like Jean Piaget and Erik Erikson theorized that humans go through stages in their development throughout life, growing from infancy to old age. Piaget outlined stages of thinking or cognitive development, and Erikson described stages of personality or psychosocial development. How can you use this information to better understand your own life? What stages of cognitive and psychosocial development have you gone through since you were an infant? Which stages will you go through as you develop into adulthood and old age?