Fwiw- one of the early indicators for us that ds was gifted at an early age was when he got a kids book of the US Presidents about 2 weeks before he turned 2. By the time he turned 2 we could turn to any page of the book and he'd clearly and accurately tell us who each president was, in or out of order. Now, that wasn't reading, just memorizing, but it was still pretty amazing to see and hear. Not something you'd see a typical not-quite-2-year-old do, kwim. He's also really good with the I spy books and computer games.
So he might not show the standard signs that would be looked for, because of where his strengths lie? Kinda off-topic but trying to justify why we feel the way we do.
