The window for languages is up to age 6, give or take a couple of months. After that it shuts down pretty fast.
It could be why as twins we could "speak" with each other and respond even before 2, but now have no recollection of it. I've listened to the tapes before and it does not make sense, but you clearly hear one speaking and one responding, the way a conversation goes.
* If twins raised in similar environments are already somewhat different, what more those raised in different environments?
Or even if we take away the twin part, are the MBTI types unchangeable throughout? i.e. whom you were as a child is who you'll be as an adult?