IQ, Belief in God, and Atheism.

Define terms: Here: theists (or "believers") are people who believe in a personal god (that is, god, God, YHWH, Allah, etc.) Athesists do not. This does not include people who believe in "a universal spirit or higher power" or agnostics.

Article: Pew Survey: Scientists and Belief
http://www.pewforum.org/2009/11/05/scientists-and-belief/

According to the 2009 Pew Research Center poll , 83% of the general population believe in God, while 33% of scientists do. [Discussion of the beliefs of scientists is based on a survey of members of the American Association for the Advancement of Science (AAAS), which partnered with the Pew Research Center on the survey.]

Oddly enough, these numbers appear not to have shifted much over the past 100 years.

Biggest hit: Evangelical Protestants are 28% of the general public and 4% of scientists. My guess is that Biblical literalism is the biggest hang up. However, I've known 2 geologists that are creationists (small "c").

Second biggest hit: Richard Dawkins who claims that only 4% of scientists are believers.

Article: Of 10 highest IQ's on earth, at least 8 are Theists, at least 6 are Christians

These are people who have both publicly known high IQ's and who have made some statement about whether or not they are atheists. Because it is a somewhat self-selected group, it hard to tell how representative it is.

The list does not include Marilyn vos Savant. She was, at one point, considered to have the highest IQ at about 228. I was unable to find anything about her views except in a roundabout way. And from what little that indicates, I would hesitate to draw a conclusion about her beliefs.

Article: Mailvox: the distribution of atheist intelligence

Vox provides several charts derived from the 2012 General Social Survey. The distribution in IQ for theists follows a bell curve. That is, believers are found at all IQ's. Or, another way of putting it, for believers, IQ has no effect on belief.

On the other hand, atheism has a very different curve. Atheism is correlated with both high and low intelligence. That is, atheists tend to be concentrated at the extremes of intelligence. There are relatively few atheists in the normal range (IQ of 85-115).

Even still, because so many more people in the US are believers, there are 10X as many belivers at the high end of IQ than atheists. 

This amused me while playing around with the GSS. Of the dumbest strata of college graduates, nearly half, 46 percent, are atheists. That's twice as many as all types of theists combined. We finally have an explanation for the Richard Dawkins fans.

I used Google to try to find statistics about Mensa and religious affiliation. My Google-fu is poor, although I did find two sources, of unknown trustworthiness, each saying that about 45-50% of Mensa members are Christian and 2-3% are Jews. [Qualifications for Mensa include being in the top 2% of standardized intelligence tests.]