The document discusses key theories of early childhood cognitive development from Piaget and Vygotsky. Piaget focused on stages of development including preoperational thinking between ages 2-6, characterized by centration, egocentrism, focus on appearance, static reasoning, and irreversibility. Vygotsky emphasized social aspects of development including scaffolding, zone of proximal development, private speech, and social mediation. Both recognized that children actively construct theories to understand the world.