I didn't have the chance to post this yesterday but there was an interesting occurrence. We were playing fetch with squeaky toys and I was signing toy then throwing it. At one point it Ranger dropped it in his wading pool. He jumped in after it and using his right paw, remember he's left pawed, dunked the toy up and down in the water using the motion/gesture for toy. It was a beautifully formed gesture repeated over and over dunking the toy. He was using the paw that is designated for signing toy even though that isn't his preferred paw. It could have been entirely random or perhaps it was meaningful. It was certainly suggestive of intentional signing. I'm glad I'm in this for fun rather than true science the question of how you know with real certainty that it is intentional signing would drive me wild.
Something interesting I'm discovering as I talk to people about teaching Ranger to sign. No one has any doubts that he can learn to read signs but for many people the idea that he could learn to make intentional signs to communicate to the humans through a shared language doesn't even register even when you're explaining that that's exactly what you're doing. For a large number of people communication with a dog can only flow one direction.