Dr. Brennan doesn't... Exactly explain things well in general terms, so I can't guarantee you'd understand it, but it doesn't have anything to do with intelligence. There's a difference between intelligence and knowledge.

[And the reason Brennan is hard to understand is that she's used to working with her coworkers and interns, who all have a certain knowledge base and are already familiar with terms and concepts. And sure, learning those terms and concepts can be more difficult to learn if someone is less intelligent, but that doesn't make it impossible and that's always something Lance thinks is important to point out.]