I wonder how much some of these differences are based on how gifted the child is in terms of memory, sensory integration and gross/fine motor control? As in, do some children need to channel more of their energy into learning motor skills? Or are they less gifted memory wise but great thinkers and therefore maybe don't seem so academically gifted as toddlers? Do do they not have the visual processing skills (as toddlers) to learn to read even if they do have the intellectual capacity (that's without even touching on dyslexia an other specific learning delays)? Personality has got to be a major factor too. Each person is so unique and the first 5 years or so of development so intense that there has got to be an awful lot of room for different ways of developing normally AND different forms of advanced development.