I would like to join the chorus of praise for Will Wilkinson's new blog on happiness and public policy. For example, this post:
Nesse goes on to point out that a few (of the far too few) longitudinal studies have shown that more positive affect is generally associated with other positive changes for individuals. But this poses a puzzle:
"If positive affect is strongly heritable [as it appears to be] and improves function [as the longitudinal studies seem to indicate], and presumably reproduction, then why did natural selection not long ago shape a higher average level of positive affect? More directly, why are there so many very successful people with many friends and resources who remain in states of chronically low mood?"
I think the answer is likely to be that what Nesse has in mind as "improved function" isn't actually improved biologically proper function, but is rather improved function relative to an internal human normative standard, and so doesn't reliably cash out in terms of inclusive fitness.
Reuven Brenner would argue that a certain type of unhappiness leads to success. Somebody feels slighted in some way, says "I'll show 'em," and strives hard at a new business.
At some point, I think that somebody has to raise the issue of treating happiness as a one-dimensional variable. Are we talking about a mood, a cognitive assessment of the quality of one's life, an outlook on the world...or some imprecise combination?