Final answer:
Erik Erikson's major contribution to the field of human development was his psychosocial theory, which suggests personality development takes place throughout a person's entire lifespan and emphasizes the role of social relationships and tasks in shaping self-identity.
Step-by-step explanation:
Erik Erikson's major contribution to the field of human development was spelling out the principle that we develop throughout the lifespan. His psychosocial theory of development expanded upon Freud's psychosexual stages, introducing the idea that personality development continues across the entire lifespan, with a series of eight stages that begin at birth and end with death. Erikson emphasized that the social relationships and the successful completion of social tasks are pivotal at each stage of development. This differed vastly from Freud's theory, which proposed that personality was largely set in early childhood. Erikson's model focuses on how our interactions with others influence our sense of self, or ego identity, and how this process continues to evolve through different phases of life.
Contrary to Freud's emphasis on psychosexual development and basic human urges, Erikson gave more weight to social aspects and conflicts. Each stage in Erikson's theory presents a conflict or developmental task that must be resolved for healthy personality development and a sense of competence. What set Erikson apart from Freud was his insistence on the lifelong process of development, suggesting that significant growth and change can occur at any stage of life, and not just during childhood.