UPDATE:
My son is now 19 months old.
- Can identify all upper and lowercase letters (I ask "where is __?" and he points). Can name at least 17. Does NOT confuse E/F, W/M, K/X, etc. Knows a few of the letter sounds.
- Knows shapes. Not just 2D (circle, square, triangle) but also some 3D (cone, cube, cylinder). Can identify rhombus (diamond) vs. square vs. rectangle even when they are all set side by side and have similar dimensions.
- Watches full-length (children's) movies.
Just like with knowing all his colors at the time of my initial post, we were blown away by how well he already knew a handful of letters at 16 mos. Just recently my Dad reminded me that they'd always said my brother was able to recite the alphabet backwards at 2 years old. I actually believe him now.
There is little doubt in my mind that my son is gifted at this point. To what degree, only time will tell. Currently, I'm already feeling simultaneous pride and embarrassment at his abilities, and I'm having difficulty sometimes identifying with mothers of children in the same age range. They talk about how their sons are super into trains ... while I'm sitting there thinking of how to explain how mine likes to smell cooking spices while I name each one or request that I write specific letters of the alphabet for him.
He still doesn't talk as much or as well as his peers, so that's the biggest thing that makes him look possibly behind others his age. But some day soon I expect he's going to catch up on that front ... and in a big way...