Actually, I’m reminded of an anecdote that I once heard. A fellow that I worked with told me that his mother worked at a nursing home for mentally challenged patients. He said that there are some patients that they can’t put together, because they will just start having sex, given time. They aren’t so retarted that they can’t do it, but are retarted enough that they can’t really learn not to do it.
I have no way of backing it up or not. I mean, I have no reason to not believe the guy. Maybe someone with more general info can elaborate.