Crucial factors in the origins of word-meaning

We have been conducting large-scale public experiments with artificial robotic agents to explore what the necessary and sufficient prerequisites are for word-meaning pairs to evolve autonomously in a population of agents through a self-organized process. We focus not so much on the question of why language has evolved but rather on how. There are many good reasons to use language once it has come into existence; for example, for establishing and maintaining group coherence, for transmission of cultural knowledge like tool use, etc. But these reasons only explain why verbal behavior is reinforced, it does not explain how this verbal behavior might emerge or complexify. Our hypothesis is that when agents engage in particular interactive behaviors which in turn require specific cognitive structures, they automatically arrive at a language system. This interactive behavior should be a natural outgrowth of cooperative behavior (if this were not the case, the behavior would be unlikely to emerge), and the cognitive structures should be simple enough to have evolved for other purposes as well (preadaptation). Our main task is therefore to identify precisely what this behavior is and what cognitive structures are required for it.