I don’t think it’s actually a question of IQ. Anyone of average intelligence can understand mathematics provided that they learn in a sequential way and they follow a well-developed curriculum. I like to believe that mathematics is logical enough so that even the most difficult concepts can be grasped if it is explained by a patient teacher.

I’d like to posit a different question: why do people of average intelligence dislike (perhaps hate, fear, and despise) mathematics?

Here are 7 possible reasons:

1. They had horrible teachers when they were little who humiliated them. Mathematics was weaponized by bitter people to bludgeon their student’s budding sense of identity.
2. They missed learning essential skills in early grades which made it difficult to understand slightly more advanced mathematical steps at a higher grade level.
3. They never got to a point where they saw the aesthetic nature of math and that nature itself appears to be entirely based on mathematical principles. (Once someone gets to this point, mathematics is as delightful as drawing, painting, or sculpting.)
4. They resorted to memorizing formulas without understanding the underlying order of any mathematical idea.
5. They were forced to do mathematics to pass an examination rather than introduced to it as a conceptual tool (probably the best one humans have ever invented or discovered.)
6. They never wondered if humankind invented mathematics or if mathematics is actually the fabric of reality that astute human beings have observed and reflected on.
7. They never marveled at the raw genius of someone like Srinivasa Ramanujan or how Issac Newton and and Gottfried Leibniz independently invented calculus during the mid 17th century. The beauty of these romantic stories about mathematics completely escapes them.