"In one of his most famous experiments, Piaget asked children, "What makes the wind?" A typical Piaget dialogue:
Piaget: What makes the wind?
Julia: The trees.
P: How do you know?
J: I saw them waving their arms.
P: How does that make the wind?
J (waving her hand in front of his face): Like this. Only they are bigger. And there are lots of trees.
P: What makes the wind on the ocean?
J: It blows there from the land. No. It's the waves...
Piaget recognized that five-year-old Julia's beliefs, while not correct by any adult criterion, are not "incorrect" either. They are entirely sensible and coherent within the framework of the child's way of knowing. Classifying them as "true" or "false" misses the point and shows a lack of respect for the child. What Piaget was after was a theory that could find in the wind dialogue coherence, ingenuity and the practice of a kind of explanatory principle (in this case by referring to body actions) that stands young children in very good stead when they don't know enough or have enough skill to handle the kind of explanation that grownups prefer.'
From Time Magazine's Top 100 Scientists http://www.time.com/time/time100/scientist/profile/piaget.html