Re: laughing question
I dont know about autistic kids not laughing ( I doubt that!) but I can tell you that 6mos is a bit too early to decide if he has as issue going on based on that alone.
Like you mentioned, all kids are diff. DS1 laughed easy and hard by 2mos..he still is a very giggly, smily boy. DS2 is a snob. His first laughter came after ds1 snorted-this after me trying to get peals of laughter out of him for so long. ANd like your dd, it takes a lot for him to smile/laugh. Everybody says that he's a quiet/calm baby. And I mutter "I know you want to ask why he doesnt smile at all!"
If there are other red flags about her, I would think of this non-laughter as a point to raise,but that alone wont suffice. SO maybe she's just a serious, broody baby.
All those crunchy things and more Amma to DS1(9.2007)