We had no clue, DS10 had a speech problem when he was younger, and so at 4 we had him tested by a speech pathologist who stated that he had a lateral slur and that he was highly gifted and that we should consider a private Gifted or HG school. We then had him tested to confirm and moved forward from there. With no yard stick to use we did not see any signs. In looking back there was only one instance that stood out. I was working on a slider puzzle on the computer and I was able to solve in about 2-3 minutes. I was teasing my DW because it took her about 6 minutes to solve. DS10 (Then 4) tried it and solved in under 1 min. At first I thought it a fluke, but he was able to solve them about as fast as I could sometimes even faster. At the time I just thought, he was good at puzzles. It never really sunk in (Even after testing confirmed it) until we had a K party and the kids wanted to play Life. DS (now 5) and I have been playing for the last couple of years. I ended up having to read all the cards and places the other children landed on to them. I got that none of them could read yet, but what surprised me was that when DS and another boy wanted to play battleships, the concept of a grid was too difficult for the other child, but DS picked it up immediately when he was 3 or so. I guess when you live with something you just assume it’s the norm.