Constructivism is a learning theory based on the idea that people actively construct their own knowledge through experiences and reflecting on those experiences. Key beliefs of constructivism include that people build their own understanding by actively experiencing and reflecting on new information as they work to integrate it with their prior knowledge, and that people learn best through collaborative activities like asking questions, exploring, and assessing their own knowledge. Major contributors to constructivism thinking include Jean Piaget, John Dewey, Maria Montessori, Lev Vygotsky, and Jerome Bruner from the 20th century. Critics argue that constructivism may not work as well with all populations or could lead to "group think".