It took me about two weeks to fully recognize and understand a uniquely Indian head movement: the bobble.
In the United States, we shake our heads “no,” nod our heads “yes,” and sometimes bobble our heads side to side to question a statement, imply confusion, or to mean “so so” or “ehhh.” Usually the US head bobble is accompanied by a shrug of the shoulders, some type of verbal cue, and/or a wrinkle of the brow.
In India, the head bobble has its own meaning. It is never accompanied by a change of facial expression or movement of the shoulders; it is done as its own, solitary action. Rather than confusion or a somewhat negative “ehhh” implication, the head bobble means “yes,” “I agree,” or “okay.” It is used everywhere by all types of people (drivers, students, shop keepers, professors) as a response to a question or to express agreement.
For the first two weeks of being bobbled at, I kept questioning the person to make sure we had reached agreement. Now, I find myself bobbling my head to indicate my own agreement with both Indians and my friends.