Abstract
Languages emerge and change over time at the population level though interactions between individual speakers. It is, however, hard to directly observe how a single speaker’s linguistic innovation precipitates a population-wide change in the language, and many theoretical proposals exist. We introduce a very general mathematical model that encompasses a wide variety of individual-level linguistic behaviours and provides statistical predictions for the population-level changes that result from them. This model allows us to compare the likelihood of empirically-attested changes in definite and indefinite articles in multiple languages under different assumptions on the way in which individuals learn and use language. We find that accounts of language change that appeal primarily to errors in childhood language acquisition are very weakly supported by the historical data, whereas those that allow speakers to change incrementally across the lifespan are more plausible, particularly when combined with social network effects.
Highlights
A language is shared by a large population, that is, the speech community: it is a set of linguistic conventions, characteristic of the population as a whole
How does the behaviour of individual speakers lead to change in linguistic conventions and the emergence of linguistic diversity? It transpires that this is one of the most debated questions in the study of language change for at least a century [1]
A widely-held view is that the locus of language change is in child language acquisition, in particular the process of inferring a grammar that is consistent with the sentences that have been heard [2,3,4,5]
Summary
Individuals in a population use language to achieve specific communicative goals, and through repeated interactions there emerge the linguistic conventions of the speech community. These conventions change over time, and as speech communities split, the linguistic conventions of the speech communities diverge, leading to variation across languages. If enough children infer a different grammar, the language changes as the generations succeed each other Variations on this basic idea exist, for example, where a child may have multiple grammars representing old and new linguistic variants, with the relative
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