Exploring feces?

How typical really, is this for a early 4-yr old? Read in a published article entitled "What it feels like to be Four" by Roberta Israeloff (a contributing editor of Parents Magazine) that 4-yr olds are increasingly interested in feces. I've noticed my daughter sometimes explores while going potty and actually inserts her finger in the back and remnants of feces are on her finger. Last night I happened to check on her at bedtime before lights out, at the precise time I saw a finger go into her mouth, and I'm 95% sure the little brown stuff I saw on her 2 molars came from her bottom. Though I'm not 100% sure, I scraped a bit from her teeth and used my own parenting judgement to determine this. (It was already bedtime, and teeth had been previously brushed clean). I plan to call our Healthy Steps nurse today to further inquire. Is there any similar stories out there that may bring me some peace that this behavior, though so disturbing, is actually a phase or interest that will pass? Further miffed by the whole thing, being overtired from a long weekend out of town, she adamantly pushed away dinner saying my chicken and pasta primavera smelled icky, and wouldn't dare put a bite of THAT in her mouth! When I asked her why she did that (the bottom exploring) she said something like "cause no one was around" which makes me sure it's something she knows she would do only when no-one was looking" PLEASE, PLEASE SEND ME ANY COMMENTS!!! I'm very concerned.

My son is almost 4 and is fascinated with his feces in terms of quantity and length. To my knowledge, he has not touched it or tried to eat it.