Those are independent clauses. Just because the individual is not talking out loud, should not be indicative that they aren't working through the problem. Personally, I am a very visual thinker and layout visual models in my head for problems with high (3-5d) dimensionality that would take longer to draw clearly in 2D space while explaining all the traversals I'm mentally making. I would then reduce a solution, and explain that, or I apologize for zoning out.
It became obvious to my office mates when I was working through and reducing a problem space, because I would "hang" on the thought. Sometimes I would be down, stuck in thought, for 15-30 seconds and according to them they could tell because my face loses emotion and my eyes flutter about.