S-Curves and the Mechanisms of Propagation in Language Change

A variety of mechanisms have been proposed in sociolinguistics for the propagation of an innovation through the speech community. The complexity of social systems makes it difficult to evaluate the different mechanisms empirically. We use the four-way typology of mechanisms proposed by Baxter and colleagues (2009), and define them mathematically in such a way that the effects of different mechanisms in the trajectory of a change can be modeled. The model suggests that the widely observed empirical pattern of an S-curve temporal trajectory of change can be captured only if the mechanisms for propagation include replicator selection, that is, differential weighting of the competing variants in a change, except under highly specialized circumstances that probably do not hold in speech communities in general.