One of the universal properties of human language is that it changes over time. Understanding the mechanisms of language change is therefore key to understanding the properties of natural language and human communication. A fundamental assumption about language change is that it originates at the level of an individual as a shift in frequencies with which a particular variant of linguistic expression is chosen over another (Sapir 1921). Conceiving of language change as the loss of an equilibrium in a system of stochastically used grammatical options, a change presupposes an emerging disturbing factor (Jäger 2007). The concept of disturbing factor is closely related to the notions of causality and actuation in language change (Weinreich et al. 1968). A change can then be viewed as an adaptation process whereby in a linguistic environment affected by a disturbing factor a hitherto marginal grammatical option begins to create a certain communicative advantage and grows in frequency. On these grounds, we might in principle expect a fast transition to the new variant in the speech of an individual, given the general learning abilities of humans (Stern 2017). However, another fundamental property of language change is that it proceeds gradually over generations. There is increasingly more evidence that the spread of a linguistic innovation over time can be successfully modelled with sigmoidal functions that grow relatively slowly over time, the full process extending over centuries (Altmann et al. 1983, Kroch 1989, Niyogi & Berwick 1997, Kauhanen & Walkden 2018). This means that the output of a speaker from generation n+1 has a frequency of an innovation that is higher than the corresponding frequency for a speaker from the generation n by a relatively small increment. Therefore, there must be powerful conservative factors at play pushing against the communicative advantage presented by the new variant. It has been suggested that the contrast between the speed of learning projected based on an individual’s cognitive abilities and the attested pace of language change (Yang’s paradox, Wallenberg 2019) may be due to the social aspect of language, whereby the communicative advantage of an innovation is balanced off by the necessity of group synchronization (David- Barrett & Dunbar 2016, Wallenberg 2019). However, since many social coordination tasks can be completed within individual’s lifetime, the question stands open which properties of language are responsible for a relatively slow group coordination when it comes to grammatical shifts. This project will develop and operationalise a novel hypothesis which states that in addition to being engaged in synchronic coordination, language speakers are cross-generationally conservative. There is currently no theory of language change unifying mechanisms of pragmatic reasoning leading to language change with both synchronic and diachronic coordination dimensions. The goal of this project is to fill this gap.
This project aims at understanding, via game-theoretic and reinforcement learning modeling, the interplay between the causes of language change in the form of emerging disturbing factors and causes of conservatism in the form of intra- and inter-generational coordination. The models will be evaluated against empirical material from three well-documented West Germanic languages.
There is a number of strong traditional intuitions about possible causal relations between certain important linguistic shifts, in particular, the relation between verbal subject agreement syncretisation and the disappearance of null subjects (Ewert 1943, Vennemann 1975) and the relation between the changes in the pragmatically motivated argument placement and the rise in the frequency of determiners (Titov 2012). Thus, verbal agreement syncretisation and changes in argument placement can be hypothesized to be factors disturbing the equilibrium in the systems of pronominal subject expression and determiner use, respectively. These phenomena form a natural class of grammatical tools facilitating reference resolution and will define the empirical scope of the project.