If happiness research can't make behavioral predictions, then behavioral research can't make happiness predictions.
Which is as it should be. Books that are based on research designed to predict behavior belong in the Social Science section. Books that tell you how to be happy belong in the New Age/Self-Help section.
If you build a model that predicts the length of marriages, you are doing social science. If you talk about whether people are happy in their marriages, then you are doing self-help.
Next, Bryan asks,
Do we calculate the unemployment rate by observing behavior? No, we call people on the phone and ASK them if they are unemployed. Is that a problem?
Actually, the household employment survey asks behavioral questions. How many hours did you work last week? Did you search for work in the last two weeks? It does not say, "How are you feeling this week: very employed, moderately employed, somewhat unemployed?"
The unemployment rate is calculated by a survey as a matter of convenience. In principle, the information could have been obtained by a third-party observer, except that would be expensive.
I think that a stronger defense of happiness research can be found in Will Wilkinson's comment entry on my last post.
There is no way out of relying on self-reports in psychology, and they have taught us a lot. When people who say they feel very stressed out turn out to have high cortisol levels, that means something. A lot of times you simply can't tell what bits of the brain do unless people tell you what they are feeling at the same time as you are looking at which bits are active. People are not VERY reliable about reporting how they are feeling, but they are reliable ENOUGH to pin down meaningful correlations between brain activity, hormone levels, etc. And this provides a basis for deeper study of the physical processes that do not depend so heavily on self-reports.
The neuroscientists may some day be able to put me on the defensive. I might have to resort to saying that what they can measure is an instantaneous chemical state, and it is a stretch to label such a state as "happiness."
What if it turns out that different people achieve the same chemical state in different ways? Maybe some people prefer being single to being married, no matter what the "happiness research" shows.
And what if it turns out that different people seek different chemical states? That is, I might prefer chemical state X to chemical state Y, even though happiness research has determined that chemical state Y is correlated with self-reported happiness in others.