When Tyler was younger, he would try very hard to get his thumb into his mouth to suck. But he never really succeeded because he had a tendency to curl his thumb in to his hand just as his hand would reach his mouth, so he just ended up sucking on the side of his hand more often than not. Eventually he discovered his fingers, and he has fallen in to the habit of sucking on his two middle fingers to sooth himself to sleep. It looks pretty funny, but hey, whatever works! 🙂