Right. And yet it's hard not to feel that swell of pride when your child 'overachieves' on some milestone. But often when a child hits a milestone early, it's actually because they are doing something differently than age-equivalent children or adults do it. And that something may well be an intellectual dead end. The niece in your story may be tagging the name 'tiger' to something like length of tail, or surrounding context. And I could write books on the need for serious investigations into what kids mean when they use certain words.