It's not like the kid is going to decypher a book called "Everything about us in 2 volumes", he'll probably just decypher some detail like "they hunt because they lost a bet" or something.
As for the kid in the movie, I have this scene in my head now, like the Predator stumbled onto the kid accidentally, the kid noticed him but wasn't scared, the Predator was confused as to why the kid is not scared and tries to break stuff and look menacing to him, but the kid doesn't budge. Eventually the Predator gives up.