In India there is a custom of clapping the hands or snapping the fingers when somebody is yawning. The idea is that yawning is the sign of the falling of the rhythm, it is the rhythm of one's body that falls to a slower rate when one feels inclined to steep, and the clapping of the hands and the snapping of the fingers set the pulsation of the other person in the same rhythm as before. It is just like shaking a person who is nodding, to bring the mechanism of his body into proper working order.