Historical change in language using Monte Carlo techniques

A system has been programmed in JOVIAL to serve as a vehicle for testing hypotheses about language change through time. A basic requirement of the system is that models must be formulated within the framework of Sapir's concept of drift and Bloomfield's definition of a speech community. Outside these restrictions, an experimenters selection of hypotheses is free. The system, which can be viewed as performing Monte Carlo simulations of group, language change, has been successfully tested in several computer runs using an extremely simple model of linguistic interaction. (The system, and any model tested within its framework, are separate entities. Accordingly, the use of a trivial model to check out the operation of the system does not depreciate its ability to handle models of vast complexity.) The initial test population consisted of fifteen adults and five children, each represented by a phrase-structure generation-recognition grammar. The grammars and the frequency parameters associated with their individual rules were not necessarily identical. During the course of a run some individuals died and others were born. Newborn children acquired the language of the community. The units of interaction consisted of conversations that were produced by the grammars of speakers and parsed by the grammars of auditors. The linguistic structure of a conversation determined changes in the auditor's grammar. Decisions in the system were made with random numbers on the basis of weighted frequency parameters. To insure control of free variables before undertaking experiments with factors causing change, the goal of the initial experiment was to obtain a condition of linguistic stability and essentially identical results for the population as a whole from several computer runs which differed only in the choice of random numbers referred to in decision-making processes. Such results were obtained; even though the fate of individual members of the speech community varied widely in the different trials, the mean values of the frequency of the grammatical rules in the total population were very similar at identical time periods in each run, for a simulated span of twenty-five years and the structure equilibrium state.