The article below makes some useful observations but I believe that the case for the "No" answer can be put even more simply:
There are two large and important nations with high levels of Christian belief where about 40% of the population are regular churchgoers: Russia and the USA. Lying geographically in between them, however, is another large group of important nations where religious observance is very low: England and Western Europe. Yet from the USA to Russia and in between IQ levels are virtually the same: About 100. That sounds like a zero correlation between belief and IQ to me.
And given the very different histories of the two countries, attempts to explain why America is different collapse into absurdity if one attempts to apply such explanations to Russia.
Another rather obvious point that often seems to be overlooked is that religion and church affiliation are not at all the same thing. I did many random surveys of various populations in my 20 year research career and religion was often one thing I asked about in my surveys. And, being a psychometrician, I exercised great care about how I asked the religion question. I always provided a considerable list from which people could choose in order to specify what their religious views were. And an option often chosen (by up to 20% of the respondents) was: "Belief in God only".
And that is a very reasonable choice. One hardly needs to refer to the sexual misconduct scandals that have engulfed the Catholic and Anglican churches to understand why many people would feel that the churches know no more about God than anybody else. The very multiplicity of denominations and faiths also suggests that conclusion. So questions about church affiliation could yield very different correlations from questions about religious belief. And there seems to be very little data on the latter.
A more cogent explanation for national differences in religious committment is that the key ingredient is not IQ but rather the presence or absence of a welfare State. Where the State provides you with cradle-to-grave security, you have less need for God. And that indeed is a stronger correlation. England and Western Europe do have much more pervasive welfare provisions than do the USA and Russia.
From a Christian viewpoint, however, welfare States could be seen as delusions of the Devil. As one writer says:
"Charles Murray, among others, has shown that welfare programs often end up being a remedy more deadly than the malady by creating the very situations they profess to cure. The simple reason for this was identified by the insightful economist Walter Williams, who said, “What you subsidize (poverty) you get more of; what you penalize (prosperity), you get less of.” Nor has the welfare state reduced crime, because crime is not primarily rooted in economic causes. It is rooted in moral causes."
So while the Devil may have deluded people into thinking that they have no need for God, that delusion will have the harmful results that one would expect from the Devil.
But from both a social science and a Christian viewpoint the idea that people most turn to God when they are most in need of him is quite uncontroversial I would think. It says nothing about God but much about people.
There are some not wholly convincing dismissals of the welfare/belief correlation here
Disclosure: (for those who are not already aware of it) I am myself an utter atheist -- JR
"Why should fewer academics believe in God than the general population? I believe it is simply a matter of the IQ. Academics have higher IQs than the general population," says Ulster University academic Richard Lynn. "Several Gallup poll studies of the general population have shown that those with higher IQs tend not to believe in God."
Hmmm. What are we to make of this? Professor Lynn and colleagues wrote a paper in 2008 in the journal Intelligence which has been widely discussed. Here is a summary of its claims:
"Evidence is reviewed pointing to a negative relationship between intelligence and religious belief in the United States and Europe. It is shown that intelligence measured as psychometric g is negatively related to religious belief. We also examine whether this negative relationship between intelligence and religious belief is present between nations. We find that in a sample of 137 countries the correlation between national IQ and disbelief in God is 0.60 [a high correlation]."
The highlight of the paper is the chart of 137 nations. And it looks pretty convincing until you study it carefully. Then, picturing the data is a cart for the theory, wheels start wobbling.
I first became suspicious when Lynn et al. tried to explain why the United States is anomalous “in having an unusually low percentage of its population disbelieving in God (10.5 percent) for a high IQ country .”
"One factor that could provide a possible explanation for this is that many Americans are Catholics, and the percentage of believers in Catholic countries in Europe is generally much higher than in Protestant countries (e.g. Italy, 6 percent; Ireland, 5 percent; Poland, 3 percent; Portugal, 4 percent; Spain, 15 percent). Another possible contribution to this has been continued high immigration of those holding religious beliefs. A further possible factor might be that a number of emigrants from Europe went to the United States because of their strong religious beliefs, so it may be that these beliefs have been transmitted as a cultural and even genetic legacy to subsequent generations. Parent–child correlations for religious belief are quite high at 0.64 (fathers–sons) and 0.69 (mothers–daughters) (Newcomb & Svehla, 1937). It has been found that religious belief has a significant heritability of around 0.40–0.50 (Koenig, McGrue, Krueger & Bouchard, 2005), so it could be that a number of religious emigrants from Europe had the genetic disposition for religious belief and this has been transmitted to much of the present population."
Good thing it’s easy to test that one. Canada has a similar history, and features average IQ 99, with 22 percent not believing in God. So twice as many Canadians don’t believe in God but exhibit no statistically significant reward in IQ. That’s one wheel off - but it’s still a tricycle.
Looking at the chart closely, I noticed another anomaly: The Czech Republic and Slovakia split on January 1, 1993. In 2008, the Czech republic clocked IQ 98, 61 percent disbelieving in God, and Slovakia at IQ 96, with only 17 percent disbelieving in God. The difference is obviously cultural. Second wheel gone. We now have a bicycle.
The third wobbly wheel was the fact that Israel and Portugal -with very different culture and histories - both feature IQ 95. But in Israel 15 percent disbelieve and in Portugal 4 percent. So tripling or quadrupling the number of atheists did nothing for IQ when culture and history are different.