Human beings communicate messages to each other in a variety of ways. In our culture it is customary to shake hands with a person whom you meet for the first time. If you refuse to do so it would convey the message that you did not accept, or that you were holding something against, the other person. Similarly, in an appropriate context, a nod or a wink, the wrinkling of the brows or the raising of a finger may serve as a means of communicating some message or other. Such means of communication may, for example, serve to indicate bids at an auction.