Hi and Bye

So, little man and I have been working on the Hi and Bye wave for a while.  For him, I do the hand-to-fist movement as the wave, instead of moving his arm back and forth.  Usually, when we say hi and bye to anyone, he smiles and ducks his head into my shoulder.  And then will turn his hand to himself and wave about 10 minutes later!  But over the weekend, we were outside and one of the neighbors, she's 10, came over and said, Hi!  And he lifted his hand and waved!  I was so excited.  Then when she went home, she came and said, Bye!  And he did it again!  Lots of kisses and cheering.  Later, we went to chipotle for dinner and I suggested that little man say hi to everyone.  Not. A. Thing.  So, in the few days since then, I've noticed that if someone says it to him, he'll do it.  But anything like a directive, no dice.  And sometimes for utter cuteness, if you just happen to say hi or bye, he'll start waving.