Do Literate People Think More Complex Thoughts

Colin Wells in Sailing from Byzantium: How a Lost Empire Shaped the World suggests (in his discussion of the transfer of literacy to Russia from Byzantium via the Cyrillic alphabet) suggests that people who can read and write learn to thing through more complicated arguments than illiterates are able to make. My book club discussed this comment briefly, with several people saying the idea was interesting.

I wonder now whether this is simply prejudice of an author from a literate society toward people in illiterate societies. Does Wells think Homer could not follow a complicated thought, or that the Iliad and the Odyssey were not complex? Indeed, it seems to me that people with trained memories who did not have a lot of things to divert their minds from complex thoughts may be better able than we to deal with complexity.