This document summarizes the constructivist contributions of several theorists including Piaget, Bruner, Vygotsky, and Dewey. It discusses key concepts from each theorist such as Piaget's cognitive stages and schema, Bruner's emphasis on readiness and a spiral curriculum structure, Vygotsky's zone of proximal development and social cognition, and Dewey's view that understanding comes from meaningful experiences. The document also outlines two principles of constructivism and how a constructivist approach can be implemented in the classroom by setting problems for student exploration and referring to primary sources.