Excerpting from an article by Reichhardt (Nature 444, 418-419; 23 November 2006) and an editorial (pp 401-402) in the same issue of nature:
Is happiness a single emotion or a personality trait? A physical state, with characteristic brain-wave patterns and biomarkers? Is it simply the absence of unhappiness, or something else? ... This new science has yet to provide a compelling account of how happiness is created. Instead, for obvious methodological reasons, it concentrates on what it correlates with. But it is not clear that changing those correlates by dictat would necessarily produce the desired effect. People may be happy spending time with their children, but forcing parents to spend more time this way would not necessarily overjoy everyone involved. Expressing gratitude makes people happier; a politeness police, probably, would not.
There is further debate as to whether trying to do something about people's happiness is feasible in principle. Some researchers favour the idea that people have a 'hedonic setpoint' that stays remarkably constant in the face of bouquets and brickbats. Such a setpoint need not in principle be unalterable, but its alteration might require an approach with a pharmacological component, raising the problem that one of the things we value about happiness is its authenticity. Another is its autonomy. Governments may guarantee citizens freedom in their pursuit of happiness, but we bridle against the idea of its ever being enforced.
Carol Ryff (University of Wisconsin) is responsible for perhaps the most ambitious well-being research project on happiness ever conducted, the Midlife in the United States, or MIDUS II, study...Ryff hopes to find out whether well-being and ill-being (depression and so on) have distinct biological correlates, or whether they are at opposite ends of the same psychological spectrum. One of her previous studies on a group of 135 older women assessed on biomarkers such as cortisol and waist–hip ratio, suggested that the biological correlates of well-being and ill-being are largely distinctive6. That's one issue MIDUS II will investigate more fully.
Ryff likes to distinguish between hedonic well-being (moods and feelings) and eudaimonic well-being, which is more concerned with factors such as having purpose in life, continued personal growth and development, and good relationships with others. In fact, Ryff rarely uses the term 'happiness'. Perhaps that's because the more scientists learn, the less precise the term has become.
That's roughly where the science of happiness stands right now — still wrestling with its own terminology. Ryff has little time for the fluffier aspects of positive psychology, which she dismisses as "a lot of PR". But one thing she and other well-being researchers can agree on is the nature of the question, "We're going after it in a serious way," she says. "In the final analysis, it's an empirical question."
(By the way, the Smiley Face is made from nanotubes of DNA; see Rothermund, Nature 440, 297–302; 2006)