I think the book informs the topic a bit. At the start of the book Michael intends to become a mathematics professor, and he can be seen as a cerebral character. Kay says that she loves Michael because he's "always fair." Fairness, though, is a mathematical calculation - it means that Michael always gives back to people what they deserve, good or bad. When Fredo betrays Michael, they're both trapped, because Michael's mind doesn't have the flexibility to make an allowance for his dim brother.

I think that one of the themes of the book is that intelligence is overrated. Paulie gets cute, Carlo gets cute, Tessio was always smarter. The dimwitted Bocchicchios make a good living and have Vito's respect.