Thanks for the article - I'll send a copy of the link to difficult child 3's speech pathologist (she sends me articles, too).
We could see something in him when he was under a year old. We had eye contact, we had smiles (maybe not many) but no language and no imitative play ("touch your nose, touch your mouth," etc). He WOULD imitate facial expressions - a game easy child 1 invented for him which taught him social skills before we knew he needed it! And his fascination for words, numbers, letters and music was obvious at six months or less. I can look back and see it in him from birth, virtually. There are some things babies are not supposed to be obsessed with! He was too young to be flicking his fingers in front of his face but flickering patterns such as sunlight through leaves on the tree would quiet him when he was crying - I first noticed this as soon as we brought him home from hospital - seven days old!