I was trying to use logical argument with a friend of mine recently, and found that she was missing my point and completely misunderstanding my position. So I wonder if there is something like dyslexia of reasoning/logic, a brain condition that makes people unable to understand and follow logical arguments.
Cognitive dissonance is often a problem when trying to convince someone of your position. Depending on the subject matter and how closely the position is held for the opposing party it can be very difficult to follow even logical well reasoned arguments. The opposing party often has a framework of reality in which they make sense of various situations or concepts. If a new concept doesn't fit within that framework there is often underlying reasons as to why the argument is unable to land. So until the deeper views are addressed you are arguing in vein.
For example in order for something you postulate to be true, it may require the opposite party to reconcile other beliefs that are deeply held in a way that they are potentially unwilling to address, or see no reason to address due to unwanted stress or emotional distress in addressing the beliefs.
Alternatively there are neurological deficits or disabilities that could make getting your point across more difficult, but at least from my experience it is often a case of Cognitive Dissonance.
So let me start off by saying that the word dyslexia is a well-defined term describing a condition typically affecting the left angular gyrus.
If you're looking for a biological condition that leaves a similar effect on reasoning, I'm afraid you've got in backwards. Humans are rational beings, but that doesn't mean we always, or even often, behave rationally.
Instead, we're often driven by heuristics, rules of thumb, that helped us survive in the bush, but fail to accurately handle larger, more abstract problems.
Another issue is identity, there have been hundreds of books discussing group identity's powerful effect on our reasoning, but to distill it as much as possible: let's say someone is an anti-pencil, for whatever reason they absolutely hate pencils, and there's a group of these pencil-hating buffoons. As they assimilate into this anti-pencil group, the pencil hatred starts to become part of their identity. Once it's part of their identity, attacking their beliefs head-on is futile.
Instead of helping them to see the fallacy of their ways, counterarguments are often perceived as a personal attack; akin to insulting your taste in music, clothes, or weight.
If you are looking for ways to help, you're actually much better off inviting your pencil-hating friend to imagine what life must be like for pencil users.
Ps: If you want to know more about why, both biologically and sociologically, people can be so immune to rationality,I strongly recommend a book: Behave, by Dr. Sapolsky.