This is a question specifically about mathematics.
All math people I've talked with like discussing problems (or math in general) with others, and most people claimed that they learned most from communication rather than from reading textbooks. My situation is, however, different. Most of the time I have math-related conversations, I find that I'm not comprehending what I'm being said, even if it's something not hard (unless I'm familiar with the topic being discussed very well). [In particular, this is true of lectures. However, I am able to understand my notes.] (I'm not sure what the reason is.) In contrast, I learn much more from books and, more importantly, from posting questions on math stackexchange. I was wondering whether this is normal, and whether this will be an obstacle in writing a potential PhD dissertation, since in that case my adviser would probably be the primary source of information, and I wouldn't be able to write a math stack exchange post asking for help.