Here's an article on the value of free, imaginative play. All very well. The ducklings are, of course, experts at free, imaginative play. They can come up with their own games that last for hours involving whatever props come to hand. (Right now they are probably destroying my bed, but they're occupied.) So, it's good for creativity, developing initiative, self-regulation, blah, blah, blah.
Except what intrigued me was to read how they measured the results of imaginative play. One way to measure how self-regulation had developed was to evaluate how well the children picked up after themselves. Apparently children who are good at complex, imaginative play are more willing to clean up their toys.
I wonder at just what age this effect strikes. It certainly hasn't happened here yet.