 Signaling systems 3 and 4 are curious. System 3 is a case where, for example, I speak in French but listen in German, and you speak German but listen in French. (System 4 swaps French and German for both you and me.) Notice that in systems 3 and 4 the players are able to correctly coordinate the response with the state of the world regardless of who gets assigned the role of Sender or Receiver.