So thinking about this IQ-range business, I suspect there is some range where a person is just close enough to sometimes be sometimes in your range, and sometimes out of it, which renders them confusing and therefore annoying. Like, if they concentrate or have studied a particular subject, they can be as good at it–or better–as you are. But on general subjects or when they aren’t particularly concentrating, they say/do (from your POV) a ton of stupid shit. As a result, you have trouble classifying these people as “smart like self” (pretty much everyone believes themselves to be smart,) or “Dumb like not-self”, and our brains probably dislike that confusion.
There is probably also a point below which, as long as the other person isn’t aggressive, we stop trying to fit them into our mental models and just accept them. We might not have great conversations with them, but we also don’t try to discuss quantum with them. Kids are like this; objectively speaking, kids are pretty dumb and we fall all over ourselves when they do something like add 5+6 without fucking up, but teenagers with their “I think I know everything” attitude really piss people off, even thought teens actually do know a lot more than little kids. I don’t think it’s just because people have an evolutionary reason to bond with their own kids, because teenagers are your kids, too, and people probably find their own teenagers more annoying than other people’s kids.
So among my near-relatives, one of them has a condition that affects their brain/cognition, and I just accept them as kinda dumb and don’t stress about it. Another seems to fall into the uncanny valley of dumb and smart, which I find really stressful to be around. (Oh really, you read a study? And you are telling me about it? And oh, yes, you misunderstood the implications. Again. I see. Yes do please keep telling me about it.) Sadly, the just-dumb relative seems to fall in the annoying relative’s uncanny valley, so annoying relative complains to me about how annoying the just-dumb relative is to them.