This is relevant but disappointing. What research? The article is well written but poorly sourced. Everything I've seen demonstrates a short-term "drained battery" effect, and nothing I've seen indicates a long-term "trained muscle" effect. Perhaps this is because the studies simply aren't long-term or large enough.

Edit: thanks to Unnamed: I see that I was wrong. http://graehl.posterous.com/evidence-that-self-control-can-be-trained-lik

I say "large enough" because I expect most people to consistently fail to do things which are difficult; we want to know what happens to people who really can try (subjectively) hard over a long stretch, and not only when especially aroused. I'd be interested to see a study design that can cause a significant portion of its subjects to enter and maintain this state.

If willpower training really can happen, but most people aren't going to reach it, then showing the exact mechanism by which it works in the small minority who can effectively train it would also satisfy me.