Since an analysis of vocabulary usage brings inconclusive evidence that the agents are using the symbols to represent natural concepts (such as beaver or bayonet), <cite>Lazaridou and colleagues</cite> next modify the game, by presenting to the Sender and the Receiver different images for each of the two concepts (e.g., the Sender must now signal that the target is a beaver, while seeing a different beaver from the one shown to the Receiver).