Head Bobble

I recently encountered the "Indian head wobble" or "bobble" for the second time in my life a few days ago at the hospital. For those who have never interacted with someone who uses this gesture it can be very confusing and even unnerving. Does it mean yes? No? Maybe? It's especially hard when you're working with a patient and there's a language barrier. Are they happy? In pain? Do they agree? According to this article, the wobble can mean anything from yes to thank you to hello depending on the speed and intensity.