Indian head shaking thingy

Anyone who had acquainted with an Indian knows what I'm talking about. It's a head-shaking motion typical to all Indians whether they're speaking Hindi, Marati, Tamil, or English. Only Indians will know exactly when to use it and how to properly interpret it. Seriously, I've been in deep contact with a lot of Indians after I met Nagi, and even now I still can't do this head shaking thing myself.

It's a complicated thing, but it's a shaking that hardly means no. Here I will list the ones I've familiar with. It could mean:

1. Yes.
Usually very brief. A head shake must at least finish ONE circle. If you start from the left side, then you'll sway towards the right side and must come back to the left side.
Example: When someone ask you if you have had dinner, you simply answer with the head shaking thing. It's simply a substitute for a nod. I wonder why the Indians don't use nod for this case. To strengthen your claim (that you have had food), you can do the head shaking thing while rubbing your belly.

2. Uh-huh
This is when you're in a conversation with someone. You can head shake for the duration of the conversation, depending of how long and how much you've understood. I figured some people just head-shake to say that they're listening. The speed of the head shake varies too. If you're interested in the topic you speed it up. It's also useful to speed up when you the guy to finish talking.

3. Hello
This is usually when you meet someone for the first time. You're shy, and really don't know what to say. At the time of introduction, while shaking hands, you also shake your head. I think it means "Nice to meet you". I think you're supposed to head shake back when someone does it. Which is frustrating in my case. Should I head shake? Would I head shake right? How fast should I go? How much swaying / to what degree to each side should I go? Oh!!! I'll give you a trick for non head-shaker like myself. Just nod and smile. Smile for as long as the head shake.

4. Of course.
It could also be used when you don't want to get yourself in trouble. For example, when someone asks "Do I look good wearing this dress?", you just head shake. Do the eye movement also. I mean, make it so big that the other person can see all the white part of your eyes.

Mind you, this head shaking thing is deadly contagious. When one head shakes, the others would follow suit. However, I think you need at least one other person apart from yourself to head shake. If the other person doesn't respond, or at least you know the other person won't be able to respond, then you naturally don't head shake. Nagi for example, never head shake when I speak. But you should see him with a bunch of Indians (yes, they all head-shakers!), then the head shake is uncontrollable. It's part of their culture which a person who associate with Indians (like myself) should understand.

Now why do I bring up this topic all of a sudden? Now, my daughter - yes, the 9 month old one - is trying to master this head shaking thing! Obviously she didn't get it from me, hey I still can't do it, I don't want to embarrass myself. Not from Nagi either I think, because he doesn't head shake around the house. But this girl was saying "Ya ya ya ya ya" (like an agreement) while shaking her head. I'm not joking. I wonder if this head shaking thing is actually in the genes! I'm yet to video tape her for this. The sleuth is on the case.