KIds with Pervasive Developmental Disorder (PDD)-not otherwise specified *do* act animated and respond to their names. I'd still look into it because the higher functioning autism is often caught when the kids are older, and then they missed the very important early intervenions. I'd take the little one to a developmental pediatrician. The older one, I'd take to a neuropsychologist. Thinking "this is will go away" unfortunately usually backfires and gets worse as the child hits school age. My son has Pervasive Developmental Disorder (PDD)-not otherwise specified and had all the early interventions, even though we couldn't get a diagnosis. until 11--we insisted he get the interventions because we suspected in spite of the professionals who said "ADHD" and "bipolar" (both were wrong). Take the childbrain assessment test. That is fairly accurate if you are honest in your answers. My son's differences became more glaring the older he got. I'm also posting a link for early onset bipolar. Do you have mood disorders or substance abuse in the family? "Quirky" relatives that don't seem to "get it?" My motto is it's better to be safe than sorry Parents are not good diagnosticians because we want to see our kids as "normal." Hugs!
http://www.childbrain.com/pddassess.html