Head Motions

As I arrived in Hyderabad, i started to notice and odd movement of the head. It seems a large number of people here are related to the bobble-head dolls. Their heads move very loosely on their necks in the same general movement as a metronome does.
This movement does not mean yes or no and sometimes is used for both (very confusing to me). It is done while asking questions, while listening, while answering.
It's fairly disconcerting truthfully, mainly because I always think they're saying no.
:P