Lexical Diffusion and Biological Evolution -Based on the Historical Change of English

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I investigated the parallels in the mechanism of lexical diffusion and biological evolution from the perspective of brain-language coevolution.(1) Lexical changeI have shown, based on the data from Thesaurus of Old English (1995) and Roget's International Thesaurus (1995), that lexical change occurs through competition and selection among near-synonyms within semantic fields. Furthermore, I have explained that lexical change is a response to cognitive selectional constraints operating on brain-language coevolution in symbolic communication. I have also tried to design a dynamic system where words may be added, transmitted and deleted by the neural network.(2) Word order changeI have claimed, based on the O(bject)V(erb) and VO with a postnominal relative clause in late Old English, that the interaction between the evolution of relative clauses and perceptual factors caused by center-embeddings actuated the change from OV to VO.I have shown that the mnemonic and attentional threshold tends to prevent the particular sets of combinatorial and sequential calculations. Furthermore, I have tried to demonstrate that center-embeddings directly affect the learnability of a language based on the connectionist simulations.(3) Evolution of vowel systemUsing Genetic Algorithm, I have simulated the adaptive process of vowel system evolution from random states to optimal states, based on fitness functions in terms of perceptual contrast and ease of production. The simulation shows not only the emergence of the vowel systems, but also the competition of variant forms in the speech community, e.g., the variation of the low vowels in Old English and Middle English.