If you want to make a character who's actually both a rationalist and not particularly intelligent, rather than simply being intelligent beyond the expectations of their position, I'd suggest having them know just a few basic heuristics, which are simple if not intuitive to wield.
They might not have the smarts to pick up all the subtle signs to know when someone is trying to con them, for instance, but they'll be the first person to think to communicate important information to avoid a conflict. And they understand the importance of being able to actually change their mind, so if they're experiencing doubts about something, their response would be to go to someone they think has good judgment and is likely to be impartial, ask what they think, and then accept that answer, even if it's not the one they would have been most comfortable with.
When it comes to writing, people are generally taught a set of "rules," but are told that really good writers can "break" these rules once they really learn what they're doing. But of course, nobody can really break the fundamental rules of good writing without harming the quality of their work, it's just that expert writers have a better sense of how the fundamental rules differ from the simpler, easier to understand formulations taught to beginners. A not-very-intelligent rationalist would probably be kind of like a beginning level writer. They know that the point of following the rules is to make good decisions, the way that a beginning writer knows that the point of following the rules is to produce good writing. But they would only be able to explain to a very limited extent why those rules lead to better decisions than their alternatives, and they certainly wouldn't be able to grasp the deeper rules underlying them, and understand what sort of situations function as exceptions to the more basic incarnations.
Keep in mind that a Straw Vulcan is what happens when a character like this is put in a situation that is an exception to their rules.
This post is to raise a question about the demographics of rationality: Is rationality something that can appeal to low-IQ people as well?
I don't mean in theory, I mean in practice. From what I've seen, people who are concerned about rationality (in the sense that it has on LW, OvercomingBias, etc.) are overwhelmingly high-IQ.
Meanwhile, HPMOR and other stories in the "rationality genre" appeal to me, and to other people I know. However I wonder: Perhaps part of the reason they appeal to me is that I think of myself as a smart person, and this allows me to identify with the main characters, cheer when they think their way to victory, etc. If I thought of myself as a stupid person, then perhaps I would feel uncomfortable, insecure, and alienated while reading the same stories.
So, I have four questions:
1.) Do we have reason to believe that the kind of rationality promoted on LW, OvercomingBias, CFAR, etc. appeals to a fairly normal distribution of people around the IQ mean? Or should we think, as I suggested, that people with lower IQ's are disposed to find the idea of being rational less attractive?
2.) Ditto, except replace "being rational" with "celebrating rationality through stories like HPMOR." Perhaps people think that rationality is a good thing in much the same way that being wealthy is a good thing, but they don't think that it should be celebrated, or at least they don't find such celebrations appealing.
3.) Supposing #1 and #2 have the answers I am suggesting, why?
4.) Making the same supposition, what are the implications for the movement in general?
Note: I chose to use IQ in this post instead of a more vague term like "intelligence," but I could easily have done the opposite. I'm happy to do whichever version is less problematic.