Their mental capacity is is that of a 12 year old, but their sex drive is the same as others their age. They definitely do not have the comprehension of their drive or the responsibility/possible results of their actions. This is why they can be so easily taken advantage of and why some parents choose to have them sterilized.
My 24 year old baby sis is mentally challenged(I'm posted about it before). I would say she has the mentality of a very innocent 12-13 year old. Her bedroom has posters of dolphins and Twilight stuff and kittens. I've never heard her talk about any boys being "cute" or anything like that. I am very protective of her and I worry about someone trying to take advantage of her because she is so trusting and innocent and she is very social with others.
My other younger brother is 26 and likely the same mentality as well(I think he has a 2nd grade reading level). All he cares about is drawing and video games.
ETA: They may have some of those desires but either my parents ignore anything that would make them think they did or they aren't aware.
This post was edited on 5/4 at 7:44 pm