Evolution of human communication method from vocal signals associated with gesture to syntactic language

To investigate the problem of how and why most members in a primeval society become using vocal signals to represent non-substantial matters such as actions, we present a simple model of communication in which speakers use vocal signals and gestures. Each desire of the speaker is represented by an expression network. Every speaker expresses his or her desire by vocal signals and gestures. Then, any speaker's desire is expressed in a three step signal. When every hearer communicates with a speaker, the hearer receives the speaker's signal by his and her own hearing neural network. At the beginning of the evolutional process, the correspondence relation between desire and signal is different for different speakers. Whether the common relations are evolved in the society or not depend mainly on the number of temporally preserving neurons in the network and reward of communication.