Holding his own bottle

We haven't been using bottles much lately as I feel I've mastered NIP (nursing in public) and even gotten over my fear of it too. Plus, he now goes 4-5 hrs between nursings so its much easier to be away for a little while without having to worry about having milk for him or pumping for me. But every once in a while I get an "owie". So I had to pump one day and gave him the bottle. Grant it, it was one of the small 2.7oz bottles, but still. He held it all his own!!! He even relaxed a bit and would let it droop a little when he wanted to rest and would push it back up to drink more when he was ready!! How the heck did he learn that when we rarely use a bottle?! Our little man is so smart!!