I didn't read any of the replies to this, and in truth, doubt many people will. However, I will throw in my $0.02 regarding the issue 😉. I'm a fairly intelligent agnostic. The people I work with are all intelligent people, as well as a number of the friends I developed during undergrad and grad schools. There is a decent mixture of religious and atheist/agnostic people in my grouping of friends, though more are non-religious. The smartest man/woman I have ever met, and I've known some Nobel Prize winners over the years, lives next door to my parent's summer home. He teaches history at a community college in the area, and is a deacon at one of the local churches. I have no idea what his SAT scores were, or his IQ, but his raw intelligence is unmatched in my experience.
IMHO, being religious or not doesn't have much of an effect on your intelligence. It may influence what direction you take with your life, history instead of physics perhaps 😉, but it doesn't alter one's intelligence.