There's a lot of talk about IQ nowadays and whether it really represents intelligence or whether certain groups, such as Ashkenazy Jews, have higher IQs than others, and then you can go into even riskier territory. I'm not qualified to talk about that but it seems to me that IQ does measure something that corresponds pretty closely to what is generally thought of as intelligence, and also that it is not as evenly distributed as certain people might like it to be. At the same time, it is perfectly evident that high IQ people can also be complete idiots when it comes to perceiving spiritual truth. They are no more likely than anyone else to be able to do that and, in some cases, may even be less likely, especially in recent years when the culture is against it and science, which is only really able to be pursued by high IQ people, is so resolutely materialistic. Perhaps high IQ people get more easily lured into abstraction, and away from simple observation, unencumbered by theory.
That does not mean that spirituality is for the stupid. It is for everyone, but in its higher aspects I do believe it is more open to the intelligent because spiritual awareness is not simply a matter of heart but of mind too. Mind or thought can get in the way of direct spiritual perception but it can also help it to become more comprehensible to itself and therefore allow a deeper awareness of it. The spirituality of an intelligent person is of a higher order than that of an unintelligent one, all other things being equal. The former is more capable of delving more deeply into the structure of reality and participating to a greater degree in the mind of God which is actually a lot of what the spiritual path is about. Simple faith is open to everyone, of course, but a deeper understanding of faith requires intelligence. This intelligence may not be exactly the same as that measured by IQ but incorporates it.
So I would say that a mature spirituality requires intelligence plus something else which we might dub SQ or spirituality quotient. An evolved human being needs to develop both but IQ without SQ is a lop-sided thing showing a lack of balanced development. It may even be a kind of retarded development. Seeing many clever and successful people as spiritually retarded puts things in a different light, doesn't it?
What is this SQ? Probably something I have just made up but it can be related to intuition. Intuition in this sense is what a person develops as he allows himself to respond imaginatively to the world, and not be limited to reason with which intuition does not conflict but which it supplements. Reason applies to the phenomenal order of being while intuition relates to that which lies behind appearance. It is a sort of direct vision into that world. SQ can also be equated to what might be described as openness of the heart which may seem rather a vague term but if we can (and should) have an open mind, then why not an open heart too? This means that you are open to the greater reality beyond the everyday mundane perceptible to the senses, and it has a connection to what has been called the feeling principle. This is not feeling as emotion but as inner resonance or feeling response to reality. A person trapped in his head will make no sense of that but a more rounded person, who knows that head thinking is only a part of the totality of ways of knowing, will understand.
Human beings can be thought of as existing in four worlds, these being the physical, the emotional, the mental and the spiritual. Some would add a vital between physical and emotional but I include that as part of the physical for our purposes here. Above these is the divine but that is beyond our concern at the moment.
We need to develop a full response to each of these levels. That is well underway for the first three but the fourth is much less understood with responses mostly ranging from basic to none whatsoever. We need to develop our SQ and the traditional disciplines of the spiritual path are there to help us do just that. The first stage, though, is to acknowledge that it exists. We won't get far unless we do that.