I had to make a comment, to your common courtesy comment. lol!  Two of my childrens first words were thank you.  I used to sit with them, and pass things back and forth, saying please and thank you.

One time, my oldest and I were waiting for clothes to finish, in a laundrymat, and he caught someones attention.  I was handing him cheese curls, as he said thank you, the lady turned and asked his age.  He was less than 18 months old.  That I remember, because there are 18 months between him and my second child, and, he hadn't been born yet.

So, yes, it is possible. :)
