The document provides an overview of three major theories of human development: 1) Erik Erikson's psychosocial developmental theory which outlines eight stages of development across the lifespan. 2) John Bowlby's attachment theory which proposes that the quality of attachment between infants and caregivers has implications for development. Bowlby identified four phases of attachment development. 3) Sigmund Freud's psychosexual development theory which proposes that childhood experiences at different ages directly influence adult personality and behavior. Freud outlined five stages of psychosexual development.