I think that, when you are bonding with NT's, there's head-nodding, smiling, laughing at things that you share in common, etc.
With AS, the bonding is in the sharing (intensely) of the same interest. There may be less of the smiling, head-nodding, laughing, and more of the idea of two people working toward the same goal or finding out more about the shared interest.
Both groups just enjoy the feeling that another person "gets it", that they understand what's going on inside your mind. I think that the smiling, head-nodding and laughing is just an indication that another person "gets it."
Kris