First, here's a diagram I made for a presentation on Artificial Curiosity at the HCI Forum 2006. It shows the simple idea behind the powerful Schmidhuber type of curiosity mechanism:
I had read about Mihaly Csikszentmihalyi's idea of "flow" in the book Satisfaction: The Science of Finding True Fulfillment, by Gregory Berns (which totally sounds like a hokey self-help book, but it's not). According to wikipedia, "The flow state is an optimal state of intrinsic motivation, where the person is fully immersed in what he or she is doing." Yesterday I came across Jenova Chen's game flOw, which is supposed to be based on the same principle. He has this great diagram in his thesis that explains flow quite simply:
Notice any similarity between this and Schmidhuber's curiosity model? Seems like the same type of mechanism; the optimal situation is somewhere between overly challenging and too simple. Intrinsic rewards for situations with maximum learning progress. Or, in the case of flow, intrinsic rewards for appropriate challenges. This seems like a major isomorphism.