Even when the duck doesn't answer at all it still often works.

I worked next to another engineer in the early eighties who was working on a different project. At tea break time we got into the habit of sitting opposite each other and explaining the problems we were having. Neither of us put much, if any, effort into trying to solve the other's problems because it often turned out that simply attempting to formulate the problem in a way that would make sense to the other party was enough to reveal the answer or at least a promising idea to try.