The document outlines major approaches to cognitive development including Piaget's and Vygotsky's theories. Piaget's theory proposes that cognitive development occurs in stages of equilibrium involving assimilation, accommodation, and equilibration. His stages include sensorimotor, preoperational, concrete operational, and formal operational. Vygotsky emphasized the role of environment and proposed the concepts of internalization and the zone of proximal development. The document also discusses cognitive development in adulthood involving fluid and crystallized intelligence.