I actually did not believe that there is a correlation tough all of the studies i found show that religious persons have a lower IQ then non religious persons.
The first thing i found was
from
http://hypnosis.home.netcom.com/iq_vs_religiosity.htm
Tough this could be disputed because there are other causes that correlate like GDP.
So i looked further and i found more interesting studies like
1. Thomas Howells, 1927
Study of 461 students showed religiously conservative students "are, in general, relatively inferior in intellectual ability."
8. Brown and Love, 1951
At the University of Denver, tested 613 male and female students. The mean test scores of non-believers was 119 points, and for believers it was 100. The non-believers ranked in the 80th percentile, and believers in the 50th. Their findings "strongly corroborate those of Howells."
13. C. Plant and E. Minium, 1967
The more intelligent students were less religious, both before entering college and after 2 years of college.
17. Wiebe and Fleck, 1980
Studied 158 male and female Canadian university students. They reported "nonreligious S's tended to be strongly intelligent" and "more intelligent than religious S's."
And there is more on the subject on this site from where the quotes come
from
http://kspark.kaist.ac.kr/...Intelligence%20&%20religion.htm
So does this mean that we atheists had it all wrong and the religious are not being stubborn and deluded on purpose they just cannot grasp reality and evidence as easily as we can.