Erik Erikson's psychosocial development theory proposes that social and emotional development occurs through eight stages across the lifespan. Each stage is characterized by a psychosocial crisis that focuses on finding a balance between two opposing forces. For example, the first stage focuses on trust vs mistrust in infancy. Successful completion of each stage results in healthy development and a foundation for future stages. Erikson's theory covers development from infancy to late adulthood.