I made a fun discovery today. There's a cute little song on one of Sadie's Signing Time DVDs and I was singing it today. The words are "I say please, please, please when I want it, share, share, share when we play, your turn is your turn and my turn is mine and we say our thank yous all of the time." Each time I said the "thank you" part Sadie would rush over and kiss me.
I think I put together why she was doing this. The sign for "thank you" looks very much like what Sadie does when she blows kisses (and blowing kisses is what Sadie does these days when anyone says "kisses"). This, added to the fact that when Sadie kisses me I say, "thank you" seems to have led Sadie to believe that the word "thank you" means "kisses." It's very cute and now I know how to get kisses!