I have a particular character who spent the first fifteen years of his life as a human experiment in a weird silly mad scientist plot. Anyway, English is his first language, but as he was taken when he was a baby (I'm not sure of the exact age, but probably somewhere between six and eighteen months), his language exposure was pretty much all from the other subjects and the lab assistants in the experiment...place. He didn't get a lot of conversation from the lab assistants, of course, and I don't imagine he had too much of an opportunity to have longer conversations with the other subjects.
So, I imagine this messes with his English development by the time he's broken out of the facility, at around age fifteen, but I'm not sure to what extent. He has decent enough listening comprehension since the lab assistants use verbal commands and instructions, but I'm more concerned with his speaking performance. How would his performance be around the time that he leaves the facility? Would his English be really broken, or would it be a matter of mixing up complex grammar and a smaller vocabulary than the average fifteen year old? Or are there linguistic issues here I'm failing to see?
Thanks in advance!