I recently had the delightful experience of talking with a very poised 12 year friend today. I have known her since she was born. About 8 years ago she was 'taking notes' during a meeting we all attend. I saw one of the sheets of paper she had written on and knew I had to have it. I asked her mother and her if I could keep it. It showed remarkable development at that age. I began to use it during every presentation and a college class I taught from that point on.
She had drawn a series of large V shapes lying on their sides and at first I thought it was a series of Vs done in one continuous string. But that was not so. She had used dark pink paper so at first I missed seeing that she had used 6 or 7 separate crayon colors. She had made one complete V, then changed colors for each of the V shapes in succession. Each V joined perfectly with no breaks showing. For a child of school age it would have been amazing to see such skill but for a child of 3 or so it was astounding. Her manual dexterity alone was remarkable. But it was more than that. Her thinking process was very advanced; she showed evidence of exploratory probing and strong analytical reasoning. (Things we will discuss later.)
I was curious about what her writing shows now. So I asked her mother for an example of her writing to see. I see that she has the same analytical and reasoning ability she showed at the young age. She thinks clearly with a direct approach to problem-solving and she is highly attentive to detail.
I suggest that you save some samples written by the young folks in your life, especially your own children, and add to them year by year. See if you see changes as they mature. Even scribbles of little ones offer clues about how their minds work so as soon as a toddler can hold a crayon you can begin your experiment.