I remember an article written by a teacher. They were recounting a potential problem child they had in their class. The child, a boy, would come up and constantly "bump" up against them. This teach finally had enough and was going to send the boy down the hall then next time. Before that happened someone told them the "bump" meant the boy wanted their attention.
After reading this I realized my two boys did the same thing. they would make small physical contact when they wanted me to focus more on them. I started responding appropiately and things were much happier.
Don't know if girls do this.
I've noticed with my son. And the boys in my group, too, not so much directed at me, but at each other, to get each other's attention. I hadn't considered it in that way, but had learned to stop letting it bug me. It's funny to me now that we had been trained to discipline for these disruptions - which in turn seem to be more disruptive. I hadn't noticed it as much among the girls, who are more verbal.