And what about all the twice exceptional babies here??? These are the kids who have gross, fine, speech, visual, feeding, or other developmental delays yet end up within the 98-99.9%. How do they factor into this study?
And what about those who are twice exceptional and receive early intervention and others who do not? A lot of variables there, particularly with those on the autism spectrum.
They were probably excluded, but DD has a ton of special needs and is still PG.
DD (8) has Aspergers, ADHD, SPD, low muscle tone, and terrible vision, and didn't walk until she was 20 months old. But she was still markedly PG as a baby. She was interested in books from the first day I started reading regularly to her, at 2 months of age. She said her first 5 words in the same week at 8 months, and at 19 months, Early Intervention rated her expressive & receptive language as being around a year ahead.
She did NOT hit any physical milestones early or perform any extraordinary physical feats, and as a first-time parent, I had no idea if she was extra alert. She WAS a champion sleeper, compared to my DS. She hit her physical milestones on time until walking, which she didn't learn until 20 months. One day I remember her physical therapist (through Early Intervention), saying, "She't too busy thinking about all the ways she might fall down and hurt herself." She has definitely muscle tone and balance issues, but she still definitely thinks herself out of doing things.
DD & DS both did a number of baby studies through the University of Washington, through the Institute for Learning & Brain Science and some other research departments. I wish, in hindsight, they gave you info on your kid's results and a copy of the final paper, because now I wonder if you could see a correlation with IQ or achievement with those early studies. But alas, they don't.
