The new child doesn't lose their sense of self by inheriting the memories, and I do see it like that. Its not the child having their consciousness erased and overwritten by another, they simply inherit the memories, likely often with built in conditioning that protects the child from those memories. It would be like me waking up every day with a few more memories of my grandfather's life. I wouldn't become him, I would still be me, but I'd have his knowledge, experience, and wisdom, which I could then choose to completely ignore.
Here's a copy of
Piaget's Four Stages of Cognitive Development, which is what suggested to me that splicing fully rationalized/self-interpreted adult memories into a brain which hasn't even developed the tools for creating memory might throw a wrench into how that development progresses.
It might be kinder just to overwrite the entire damn brain from a newborn to an adult state -- which is what a full personality transplant (as GoGo described above) would do.
Come to think of it, I'd almost feel sorry for the adult who woke up in that situation. "Wait a minute! I was a captain of industry! A leader of men! What do you mean I don't even have sphincter control, and I'm going to have to wait at least six months before I can articulate clearly? And where are my TEETH?"
