Marotta, this isn't about my not liking the studies, and certainly not about not understanding the subject matter (please remember that we are in my area of formal expertise... I've actually had classes devoted to the measure of intelligence and classes devoted to the way psychological tests are created and administered. What about you?)
Let me put if very simply. I don't believe that they are measuring intelligence. I don't believe they have defined "satisfaction with your life" in a sufficiently objective fashion - their likert scale doesn't get the job done.
I also have problems with the various forms of self-reporting measurements. If we want to say that there is a form of "satisfaction with your life as a whole" that is real, we should also recognize that self-reporting is subjective and there are some serious issues regarding the accuracy with which the objective element in question is measured by this subjective approach.
It would be like someone defined "intelligence" as measurable by the number of hours one had in formal schooling, and then took a poll on how much people liked to party (say one a scale of 1 to 5?), and deduced from the resulting statistics that people who partied were more intelligent, or, perhaps, that partying led to higher intelligence. At the end they could always say, "...we cannot rule out an opposite causal order to what we hypothesize..."
Here is a real life example of an abuse of self-reporting as a measure. There are a series of studies that were done where the researcher set out to determine if self-esteem had any relationship to success. One study was conducted in prisons. The prisoners were asked, I believe, 5 questions to self-report their beliefs about how confident they were, and how high their self-esteem was, and from that, using a likert scale, like this study did in their claim to have measured satisfaction, they decided that convicted inmates showed higher levels of self-esteem than average people who had never been convicted. When you work with people it becomes important to find ways to weed out the subjective.
I have been talking about the processes we see in much of the research coming out of the social sciences. I don't have to read this paper to do that. I have no interest in reading a paper that pays great attention to regression analysis of dependent variables but not to the definitions of the objects they claim the numbers represent.
My question is this: Do you deny the truthfulness of the conclusions of the study?
Do I think they are engaged in a purposeful deceit? No. I see no evidence that they are lying. But that doesn't mean that the study automatically represents an objective truth about reality. You quoted this from the study: "...we cannot rule out an opposite causal order to what we hypothesize..." So, they don't know if 'A' caused 'B' or if it was 'B' that caused 'A' and, by the way, they have no definitions of what 'A' or 'B' actually are. The two elements you've written about are "satisfaction" and "intelligence" - does anyone think it would help to say what there actually are? A study has to make sense, its key assumptions have to be sound, its key elements defined, otherwise it is hasn't a claim to "truthfulness."