My DD took her time with the waving too. I'm always amazed when I go out and a 10 month old is waving their little hand off at me. I don't think DD waved until like 15 months, and even then she's very stingy with it, she's just not as friendly as some I guess, lol! But really, sounds good to me! Who knows why they'll do A at one age and take their sweet time with B. They are their own little people, with their own interests.