Read from a book that thumb sucking is an important form of oral stimulation and self-soothing behavior. It says: The fact is, whether or not you like the idea, sucking is what babies do, and it's something we should encourage. Remember that this is one of the first ways in which your infant gains control over his body and his emotions. When he discovers that he has a thumb and that sucking on it can make him feel better, it gives him a fantastic sense of control and accomplishment. One's thumb is always on hand it can be put in and taken out at your baby's will. The author assures that your baby will give up his thumb when he's ready.