All the studies had some form of measurement of intelligence and some form of measurement of religiosity. Of course they're not all the same but that's not an argument to dismiss them, simply a limitation to note. It could just as easily be a strength - different methods producing similar results can indicate robustness.
Unless some of these correlates are not actually measuring what they're purported to be. If your religiosity measure is not actually a genuine correlate of religious belief, but is measuring something else negatively correlated with intelligence for a different reason; then it's not an independent support for the correlation. It's spuriously making the correlation look stronger than it really it.
Oh come on! None of us have time to read and analyse the source material for every article we come across in our musings - most here don't even have access to the base papers. I lost my access 12 months ago when my last period of study ended. The best we can often do is point to an article that has made it into the general media and leave it at that. Of course if it becomes contentious, then we look further.
I have so far only skim read the paper that you found but it has all the hallmarks of being pretty thorough and it's published in a decent enough publication. The researchers found "a reliable negative relation between intelligence and religiosity". I'm not seeing any reason to throw away the overall conclusions.
I'm not suggesting we throw anything away - I'm suggesting we proceed with caution. This means considering alternative explanations for the results. I already suggested the one that I consider most likely (that people with higher IQ are more likely to differ from convention - whatever convention happens to be). Given that the metastudy is dominated by studies of Americans; this idea is not tested.
Another explanation for the correlation (the one favoured by the authors of a review on the literature on this topic
which I found whilst searching for the original metastudy) is that it is simply explained by education; mediated by the fact the religious fundamentalists are likely to receive less formal education than the general population. The metastudy does
try to test this idea and their findings are not supportive. However, it's no longer an impressive metastudy, since only 6 of the included studies* have the necessary data.
*4, really, but they count separate data sets within the same study as independent studies
ABE: What I am trying to say is not that this study is nonsense. Rather, I'm saying that jumping from this to "Atheists are more intelligent than Religious people" is doing the same as news editors do when they tell us that grapes cause and/or cure cancer due to a suggestive study that establishes no such thing.
Edited by caffeine, : No reason given.