Competition, selection and communicative need in language change: an investigation using corpora, computational modelling and experimentation
Constant change is one of the few truly universal cross-linguistic properties of living languages. In this thesis I focus on lexical change, and ask why the introduction and spread of some words leads to competition and eventual extinction of words with similar functions, while in other cases semantically similar words are able to companionably co-exist for decades. I start out by using extensive computational simulations to evaluate a recently published method for differentiating selection and drift in language change. While I conclude this particular method still requires improvement to be reliably applicable to historical corpus data, my findings suggest that the approach in general, when properly evaluated, could have considerable future potential for better understanding the interplay of drift, selection and therefore competition in language change. In a series of corpus studies, I argue that the communicative needs of speakers play a significant role in how languages change, as they continue to be moulded to meet the needs of linguistic communities. I developed and evaluated computational methods for inferring a number of linguistic processes – changes in communicative need, competition between lexical items, and changes in colexification – directly from diachronic corpus data. Applying these new methods to massive historical corpora of multiple languages spanning several centuries, I show that communicative need modulates the outcome of competition between lexical items, and the colexification of concepts in semantic subspaces. I also conducted an experiment in the form of a dyadic artificial language communication game, the results of which demonstrate how speakers adapt their lexicons to the communicative needs of the situation. This combination of methods allows me to link actions of individual speakers at short timescales to population-level findings in large corpora at historical timescales, in order to show that language change is driven by communicative need.