I think "giftedness" is as complex and individual as people themselves. Alot of it has to do with interest (passion even), readiness to learn, the speed at which they seem to process the information, the depth and breadth of their questions, etc.
I still take it for granted that all children would be able to read at least simple books like Green Eggs and Ham when they ENTER kindergarden. Apparently this is NOT the norm. But I also don't get it. Even if you barely interact with your child, how hard is it to park them in front of Sesame St or Dora instead of Spongebob or Rugrats? Or even pop in a Baby Einstein DVD?
I sew and craft for a living and DD8 has always really LOVED to go to the fabric store with me. She can give you a whole range of names for shade of colors (salmon, hot pink, fuschia, magenta, etc). DD4.5 was an early talker, how early, I don't actually remember, lol? But I was ALWAYS explaing what I was doing "I'm choosing some delicious broccoli for dinner, let's put it in the cart. What else should we buy?" You know the drill. She is quite the wordsmith and is very precise in descriptions. I can absolutely see the influence of choices I have made...but if they weren't "gifted", they would just absorb the info, I feel. Acceptance vs questioning is the difference I think...