What do we learn through Art Education - beside the arts?

It seems that children can learn quite a lot though rich art education. E.g. Anne Bamford claims that they (also) learn literacy and math, and James Catterall tells us that it even helps us get jobs and friends better.
On the other hand: A lot of such claims are already muted by research at Havard University, among these the so called Mozart effect.

Where do we find 'hard' evidence that it is possible to develop empathy, intelligence, creativity, literacy etc. through art education? Can anyone suggest some literature from recent research projects?