Answer:
theory
Step-by-step explanation:
Jean Piaget had done previous research on how children grow and develop some patterns and skills. Then he identified some stages of development that will lead him to connect many concepts and behaviours into a theory of learning. The inquiries led him to make a hypothesis that he verified by observation directly working with children of different ages.
The result was the theory known as the four stages of development and the so-called constructivist approach in pedagogics.