My baby boy is almost six months old. He opens his mouth nicely for a bite of cereal, but he seems to like washing it down by sucking his thumb with each bite. I say "with" because he won't even wait for the spoon to get out of the way. This has been going on for a couple of weeks now. Do you think he's doing it for comfort? (He only eats cereal once per day right before bed, making it part of our nighttime ritual, so that's why I think it may be a comfort thing.) To help him swallow or to help the food go down? Any other ideas? Ever heard of this before?