I don't have subvocalized thoughts, but I do know when I'm thinking. It wasn't that, it was like recalling a memory. I thought about the problem, and then the memory of the solution came.
Oh, interesting. Lots of people that have subvocalized thoughts (which is most people it seems) identify with them so strongly they think it’s who they are.
I find this works extremely well.
It can really be a tactic to overcome some things that probably could not be solved any other way.
That's the kind of rest I like to get, where you make progress at the same time ;)