Each agent has a table which relates words (symbols) with meanings. Simple commmunication games, which represents an essence of the communication system observed in the research on vervet monkeys, have evolved the vocaburary (relationship between words and meanings) in the population. The point here is that unity of the vocaburary is not always good in adaptive sense under the condition of reduced resources and poor communication abilities. Therefore, the states of word unity are broken by invasion of new words as shown in the upper graph. The lower graph shows that agents receive lower scores in the states of word unity than in the states of coexistence of several words.
