Happiness research cannot make behavioral predictions at all. It consists of taking meaningless surveys, and the most it can do is make predictions about the "findings" of other meaningless surveys.
This reminds me of the old saying, "What good is happiness, can it buy money?" If happiness research can't make behavioral predictions, then behavioral research can't make happiness predictions. It's hardly obvious that one is more worth knowing than the other, still less that knowing about happiness is worthless.
Or is Arnold saying that talk about happiness is inherently "meaningless"? All I can say in response is that it seems perfectly meaningful to me. When someone says "I feel happy today," or "I have led a sad life," I know what they mean. Don't you?
If you ask somebody to rate their happiness on a scale, you have no idea what the answer means. Are respondents reporting a feeling, or an evaluation of how they think they ought to feel? Are they reporting something instantaneous, or something that also combines looking backward and/or forward?
There is some ambiguity in all questions. The obvious solution is to fiddle around with the wording and see if the results change. Happiness researchers have done this to some extent. If you think they haven't done good enough, then you should tell them the Right Way to Ask.
Incidentally, the same problem arises in ALL economic statistics. 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? Of course. Does it make unemployment numbers meaningless? Hardly. Imperfection does not imply worthlessness. When you decide how much weight to put on any statistics, you always have to make a judgment call about the extent to which respondents had the desire and/or incentive to lie.
You have no more basis for saying that "Married people are happier than single people" than you do for claiming that Bernie's marginal utility from the millionth scoop of ice cream exceeds my marginal utility from the first bread crumb.
Sure I do. While I can see why people might exaggerate their happiness, it's hard to see why married people would be more inclined to exaggerate than single people. In contrast, Bernie had a clear motivation to lie about his marginal utility of ice cream - to make other economists praise his sense of humor.