The young Indian chief was at a loss. He was asked by his people if the winter would be cold or mild, but he hadn’t learned the ways of predicting the weather of his ancestors. To buy time, he told them to gather the firewood anyway and, behind their back, called the National Weather Service and asked if the winter would be cold. “Looks like it,” was the answer.
So the chief told his people to gather more firewood, and after a week called the national institute to confirm their opinion. Because they sounded more confident about the cold winter, the chief told his people to gather even more firewood.
He called the national institute again after a while to make sure of their view of the cold winter, and knew that they were now predicting the coldest winter on record. Asked the basis of their prediction, they gave it away that the Indians were collecting firewood like hell.
It was then that the young chief found out what had been going on. The forecast of the national institute was based on their observation of the activity of them Indians, and, when the Indians acted according to the forecast, the national institute was modifying their forecast accordingly. He had no way of knowing it, but the Indians and the national institute had constituted a positive spiral the economists in the civilized world were talking about.