I wonder this again today as I read blog posts with babies that are very close to the same age as my Jack.
Other babies are sitting up on their own. Jack does for a few seconds and than topples over.
Other babies are pulling themselves up on their toys or in their cribs. Jack doesn't do this and hasn't even tried yet.
Other babies laugh like crazy. Jack only laughs when he's tickled. He's a very serious (grumpy) baby.
Is my baby slow? I am trying not to compare, but it's really hard. I try practicing things with him like sitting and "walking". I read to him every night. I sing to him. We talk about our day. I point out things when we are driving in the car. He gets socialization.