Is it naive of me to think about how happiness fits in here? I don't know that there's a correlation between intelligence and happiness; I think intelligence grants one a deeper understanding and keener appreciation of both the goodness of good and the badness of bad: one sees more how and that the world is wonderful to the same extent that one sees more how and that the world is horrible too.

But I think there is a correlation between goodness and happiness. I don't think that bad people can be happy, not really happy. But maybe what it is is that bad people don't miss happiness, or understand it, or want it in the first place, or that other pleasures -- being "right," feeling superior to, etc. -- are more important to them.