Final answer:
The theory based on Piaget's ideas of experiential learning and actively constructing mental models is called Constructivism.
Step-by-step explanation:
The theory that is based on Piaget's ideas of experiential learning, where individuals are engaged in actively creating things and constructing mental models, is called Constructivism. Constructivism is an extension of symbolic interaction theory, which proposes that reality is what humans cognitively construct it to be. In the context of education, this theory suggests that individuals learn by constructing their own knowledge and understanding through hands-on experiences and interactions with their environment.