I agree with the Dude.
My 18-month-old that knew all of that stuff is three years old now. In my experience, some kids are just not exposed to that stuff at an early age. They are not interested, and good parents follow their babies' interests. And, then some kids, like ours, gravitate towards this type of learning at an early age.
For me, it wasn't that DD could learn letters, colors, shapes, etc. at 18 months, it was that she seemed to be hungry for the rote memorization that these things provided. And, it continued. I felt like we had to feed her need to memorize up until about 2.5. Then, in the span of about one month, reading, counting, and math really clicked. Coincidentally, at about this same time she became interested not so much in just memorizing, but thinking critically about science and history. Now, she still memorizes a lot, but we are blown away by what she can understand.
My DD cannot do jigsaw puzzles very well. Because she does not gravitate toward them, we do not expose her to many puzzles. So, her exposure to puzzles is low BECAUSE she is not very good at them.
