Which psychologist proposed the Theory of Cognitive Development and Constructivist Theory describing how children construct mental models of the world?

• A. Jean Piaget
• B. Erik Erikson
• C. Lev Vygotsky
• D. Maria Montessori

Answer: (A)

The main idea being tested is who described how children actively build their understanding of the world by forming and revising mental models as they interact with their environment. This is Jean Piaget. He outlined a theory of cognitive development with stages—sensorimotor, preoperational, concrete operational, and formal operational—showing how thinking changes qualitatively as children grow. He also championed a constructivist view: children are active learners who create knowledge by organizing experiences into schemas and adjusting them through assimilation and accommodation, moving toward equilibrium. Other figures differ in focus: Erik Erikson mapped psychosocial developmental stages across the lifespan, Lev Vygotsky emphasized social and cultural mediation of learning, and Maria Montessori highlighted an educational approach with a prepared environment, rather than a stage-based theory of cognitive development.