Baby Sign Language Works?

So about 7 months ago we tried to teach Christian sign language. We did the signs over and over to him for months and he would just look at us funny and never do them back. Finally after months of trying we gave up. Then 2 months later, out of no where, I walked into the kitchen and Christian was hanging on the fridge door doing the sign for "eat". At first I thought it was just a coincidence, but then he kept doing it all day whenever he wanted something to eat! It's amazing that he can communicate his basic needs now without screaming. A few days ago he was sitting in his high chair eating lunch and he started to do the sign for 'eat', I looked at his tray and he still had food on it, so I told him that he already had some. He looked at me and then did the sign for 'more', so I asked him what he wanted more of, and he picked up his apple and shook it at me. So I gave him another apple slice and he was happy. This is way better than when he would just scatter the food off his tray until you put something on that he wanted. He can do a few signs now, and he has also started saying a few words too! His latest word is doughnut. Unfortunately we ran out of them and that made him quite upset. He says new words all the time and it is so fun!