What''s interesting?

Interestingness depends on the observer''s current knowledge and computational abilities. Things are boring if either too much or too little is known about them --- if they appear either trivial or random. Interesting are unexpected regularities that seem easy to figure out. I attempt to implement these ideas in a ``curious'''', ``creative'''' explorer with two co-evolving ``brains''''. It executes a lifelong sequence of instructions whose modifiable probabilities are conditioned on both brains --- both must {\em agree} on each instruction. There are special instructions for comparing computational results. The brains can predict outcomes of such comparisons. If their opinions differ, then the winner will get rewarded, the loser punished. Hence each brain wants to lure the other into agreeing upon instruction subsequences involving comparisons that surprise it. The surprised brain adapts. In turn, the other loses a source of reward --- an incentive to shift the focus of interest. Both brains deal with the complex credit assignment problem using the recent Incremental Self-Improvement paradigm. Extensive simulations include an example where curiosity helps to speed up external reward.