Cognitive development theories of Piaget and Vygotsky are summarized. Piaget believed development occurs through maturation and interactions. He outlined four stages of cognitive development. Vygotsky emphasized social interaction and culture in development. He introduced the concept of the zone of proximal development. Both theorists see an active, developing child and complex interactions influencing learning, but Piaget focused on individual development while Vygotsky stressed social and cultural aspects.