A loose one. Those who lack the intellect to make sense of the world are more likely to place their faith in higher powers as it involves a lot less thinking; any question too complex for that person to answer can be ducked by saying, ”I don’t know but God dies, and that’s good enough for me!” without any sort of critical thinking at all.
However, while those on the other end of the scale are more likely to see their own answers rather than rely unquestioning obedience of religious dogma, some of high intellect maintain faith and merely ask deeper, more thoughtful questions. Newton had both faith and intellect, and his quest for answers about the nature of the universe led him to ask some pretty deep questions, furthering math and science considerably in the process.
I’d say that there is a stronger correlation between one’s curiosity and whether one has faith or not. Those of lower intellect lack curiosity because asking questions one cannot understand the answers to highlights one’s shortcomings. For those people, it’s safer to just find someone who tells you what to believe, echo their dogma, and avoid the whole thinking thing entirely.
@JLeslie Most of the intelligent people I know are agnostic for reasons that are summed up by J.B.S. Haldane’s famous quote, “My own suspicion is that the universe is not only queerer than we suppose, but queerer than we can suppose.”. Religion serves an important psychological need for things to make sense, but not everyone is willing/able to take someone else’s word when they say, “The universe works like this….”. And for some, the urge to not be wrong is far stronger than the urge to be right; by not following any religion, you’re less likely to be wrong than if you had a totally incorrect assumption of how things are.