Paraphrased from The Effect of Intelligence on Religious Faith, Burnham 
P. Beckwith, _Free Inquiry_, Spring 1986:

1. William S. Ament, 1927 
C. C. Little, president U. of Michigan, checked persons listed in _Who's
Who in America_: "Unitarians, Episcopalians, Congregationalists, 
Universalists, and Presbyterians are ... far more numerous in _Who's 
Who_ than would be expercted on the basis of the population which they 
form.  Baptists, Methodists, and Catholics are distinctly less numberous."

Ament confirmed Little's conclusion.  He noted that Unitarians, the 
least religious, were more than 40 times as numerous in _W'sW_ as in the 
U.S. population.

2. Lehman and Witty, 1931 
Identified 1189 scientists found in both _Who's Who_ (1927) and 
_American Men of Science_ (1927).  Only 25% in _AM of S_ and 50% of 
those listed in _W'sW_ reported their religious denomination despite the
specific requests to do so, "religious denomination (if any)."  Well 
over 90% of the general population claims religious affiliation.  The 
figure of 25% suggest far less religiosity among scientists.

Unitarians were 81.4 times as numerous among eminent scientists as 
non-Unitarians. 

3. Kelley and Fisk, 1951
Found a negative (-.39) correlation between the strength of religious 
values and research competence.  [How these were measured I have no idea.]

4.  Ann Roe, 1953
Interviewed 64 "eminent scientists, nearly all members of the 
prestigious National Academy of Sciences or the American Philosophical 
Society.  She reported that, while nearly all of them had religious 
parents and had attended Sunday school, 'now only three of these men are 
seriously active in church.  A few others attend upon occasion, or even 
give some financial support to a church which they do not attend... All 
the otheres have long since dismissed religion as any guide to them, and 
the church plays no part in their lives...A few are militantly 
atheistic, but most are just not interested.'"

5.  Francis Bello, 1954
Questionaired or interviewed 107 young (<= 40) nonindustrial scientists 
judged by senior colleagues to be outstanding. 87 responded.  45% 
claimed to be "agnostic or atheistic" and an additional 22% claimed no 
religious affiliation.  For 20 most eminent, "the proportion who are now 
a-religious is considerably higher than in the entire survey group."

6. Jack Chambers, 1964
Questionaired 740 US psychologists and chemists. He reported, "the 
highly creative men [jft- assume no women included] ... significantly 
more often show either no preference for a particular religion or little 
or no interest in religion."  Found that the most eminent psychologists 
showed 40% no preference, 16% for the most eminent chemists.  

7.  Vaughan, Smith, and Sjoberg, 1965

Polled 850 US physicists, zoologists, chemical engineers, and geologists 
listed in _American Men of Science_ (1955) on church membership, 
and attendance patterns, and belief in afterlife. 642 replies.

38.5% did not believe in afterlife,  31.8% did. Belief in immortality was 
less common among major university staff than among those employed by 
business, government, or minor universities.  The contemporaneous Gallup 
poll showed 2/3 of US population believed in afterlife, so scientists 
were far less religious than typical adult.

From Beckwith's concluding remarks:

      Conclusions
      In this essay I ahve reviewed: (1)sixteen studies of the 
      correlation between individual measures of student intelligence and 
      religiosity, all but three of which reported an inverse 
      correlation. (2) five studies reporting that student bodies with high
      average IQ and/or SAT scores are much less religious than inferior
      student bodies;(3)three studies reporting that geniuses (IQ 150+)
      are much less religious than the general public (Average IQ, 100),
      and one dubious study,(4)seven studies reporting that highly 
      successful persons are much less religious in belief than are others;
      and (5) eight old and four new Gallup polls revealing that 
      college alumni (average IQ about 115) are much less religious in 
      belief than are grade-school pollees.

      I have also noted that many studies have shown that students 
      become less religious as they proceed through college, probably in
      part because average IQ rises.

      All but four of the forty-three polls I have reviewed support 
      the conclusion that native intelligence varies inversely with 
      degree of religious faith; i.e., that, other factors being equal,
      the more intelligent a person is, the less religious he is.  It 
      is easy to find fault with the studies I have reviewed, for all 
      were imperfect.  But the fact that all but four of them 
      supported the general conclusion provides overwhelming evidence 
      that, among American students and adults, the amount of religious
      faith tends to vary inversely and appreciably with intelligence.


I would like to add a few opinions of my own concerning intelligence.  I 
doubt that innate intelligence varies much among individuals at birth.  
One has wetware that either works or is defective in some way 
(mental retardation).  We see in various guises the effect of training 
on IQ, e.g., teaching 6th grade students the game of WFF 'n Proof raises 
measurements of mathematical thinking almost a full standard deviation 
from the initial measurement.  Intelligence seems to be learned (by most
of the numerous studies I have seen), and, prior to the concrete that sets 
in during the early 20s, can be improved quite a lot. The earlier the 
process begins, the higher the resultant IQ.  I cannot remember them 
specifically, but I have read studies which showed a disproportionate 
number of superior/genius among children who's parents raised them with 
purposeful efforts to increase their ability to think and solve 
problems.  The most famous case would be that of John Stuart Mill, who's 
father read to him constantly from the time he was born, constantly 
teaching him, day and night and in the child's sleep, even.  John S. 
Mill could read Greek at the age of 4, and remains the highest scoring 
writer on syntactic analysis of sentence structure/vocabulary versus IQ.

In sum, the fatalistic concept that we are born with some preordained 
intelligence level seems ill-founded.  That it ceases to increase after 
adulthood is part of the maturation process that freezes our brains into 
a cognitive concrete before the age of 30.  IMHO, if one has not become 
"intelligent" before 20, nothing will help.

Are there highly intelligent Xians?  Most certainly, but they do not 
apply their reasoning to religion.  Perhaps the best hypotheses to 
explain the phenomenon of the intelligent professing deep religiosity are
1) Ignorance.  Intelligence does not imply correct information.
2) Compartmented personality.  The scientist and the prayer-maker never meet.
3) Knavery.  The statement of belief is a sham to serve another purpose.
4) Fear of censure by friends and family.
5) Delusions or insanity.