Well it is a "natural act" and everybody has done it at some point in their life and if you say you haven't ... Well.... Your not telling the truth..... Now while I wouldn't allow a child to sit on my couch or lay in the middle of my play room and pleasure themselves but what they do in the playpen by themselves while going to sleep is up to them. Now I believe soothers and thumb sucking are vile habits but I have one child that sucks her thumb and plays with her hair while going to sleep .... Should I tie her hands behind her back?