Deludedgod, or anyone else who is expert in this kind of thing: Can you give me a brief synopsis of what's going on in our brains when we do an altruistic act that is not particularly pleasant, but gives us a feeling of calm happiness? For instance, I really hate doing masonry, but I helped a friend build a retaining wall once because he couldn't afford to pay anyone to do it. Ordinarily, I would be in a foul mood, and a great deal of physical discomfort. In this case, I hardly noticed the blisters on my fingers, and the time passed much more quickly than if I were just working for pay.

What triggers this kind of experience? Is there such a thing as a layman's explanation of how this kind of adaptation became an evolutionary advantage? I know Dawkins has written a good bit about altruism, but I don't think I've ever read anything about the specific neurology of it.