In India, an American is likely to be confused by the gesturing of heads in regards to nodding yes versus nodding no. My source first encountered this phenomenon on a trip to India for business. He explained how communicating with the native people was rather difficult, especially when asking questions. In the United States, a vertically lined head nod represents a yes, while a horizontal one, no. In India, however, my source claims that it was quite different. A nod yes was more of a head bobble, and a no would be a more vertically situated nod. My source said this was extremely confusing when ordering food, in that waiters would nod their head in agreement, yet he assumed they were disagreeing with him instead.
The impact of such a simple gesture appeared to have an unexpectedly large impact conversationally, simply due to cultural preferences and meanings attached to certain movements. When asking my informant whether or not the gestures appeared to have any subtle connotations, he replied that it seemed to bear a more passive stance and less clearly defined head nods. Whether or not this is actually the case is hard to tell, nonetheless, the gesture was certainly a culturally ingrained movement that was passed on simply by immersion and association from others.