My memory on this one is very, very fuzzy, but here is the story as best as I can recall.
A very young boy is living in a room or small dwelling that is actually a test lab of sorts. The boy is under observation by - I think - some sort of alien race. It may be that the aliens were trying to learn more about humans, but I can't recall for certain. I do recall for certain that the experiment is ongoing, and covers several years of the boy's life.
The story is told in the 3rd person from a narrator's perspective. I don't recall any dialogue from the boy himself. I can remember two details, both of which, for lack of a better term, might be a little bit on the "icky" side.
The first detail involves the boy "exploring his urges" as he enters puberty. Nothing explicit, but there is a line about the boy feeling ashamed afterwards.
The second detail takes place not too long after the first (I believe he's a bit older, though) and a teenage human girl is introduced to the environment. I don't know there was ever any dialogue between them, but they do become lovers. Again, the descriptions weren't sexually explicit, though there were sensory descriptions that seemed to highlight the boy's inexperience with human interaction and a certain wonder what was taking place.
I don't remember how the story ends or if there was a greater purpose to the experiment. As I mentioned before, my memory of this one is quite vague.
I read this one in a sci-fi magazine. The subject matter makes me think Omni, but I seem to recall it being something more along the lines of Analog or the like. I read it in the 1980s, but the story could be older than that. I would guess no earlier than late 60's-early 70's.