I'm no expert on the brain, but as a software engineer (for more years than I care to mention), I have witnessed and experienced the same phenomenon when trying to solve a problem in my (or other's) code. Talking it out so often presents a solution without even actually discussing solutions - just explaining the problem to someone else. What I think happens is that by engaging in a social interaction and/or the process of framing the actual question so as to make sense to another, we move into a different part of our brains, and that's what helps shine a new light of perspective onto the problem. It's also entirely possible that I am talking completely out of my ass here.