Now I'm no child development specialist, but to me, this is significant. Nate clearly must be watching his big brother and observing his interests and actions at some point. Not that they're hard to miss, ha. And he is IMITATING them! I snagged the below diagram from the Autism Speaks website, as I think it shows a good general overview of symptoms. Except I think it's time for them to move GI disorders and immune dysfunction just a titch closer to the center of this diagram. There is too much overlap for them to remain "outliers" at this point.
Also from the website:
Typically developing infants are social by nature. They gaze at faces, turn toward voices, grasp a finger and even smile by 2 to 3 months of age. By contrast, most children who develop autism have difficulty engaging in the give-and-take of everyday human interactions. By 8 to 10 months of age, many infants who go on to develop autism are showing some symptoms such as failure to respond to their names, reduced interest in people and delayed babbling. By toddlerhood, many children with autism have difficulty playing social games, don’t imitate the actions of others and prefer to play alone. They may fail to seek comfort or respond to parents' displays of anger or affection in typical ways.
Now, other than his responses to mom and dad, this has described Nate to a tee. Well at least from age 15 months on. However, he is imitating Jack these days. He "flies" the planes, he LOVES Wall-E. When he gets home from ABA he runs straight for Jack's toys, the "forbidden territory" and plays till his little heart is content. Sorry Jack. Take that autism!