Periodic Reporting for period 4 - ELC (The evolution of linguistic complexity)
Reporting period: 2021-03-01 to 2022-02-28
Humans learn the language of our speech community based on observing their utterances and the way in which they are used, inferring the underlying system of rules which govern how linguistic forms are constructed, the meanings those complex utterances convey, and how form and meaning are related. Consequently, language undergoes cultural evolution: it changes over time as a result of pressures applied during learning and use. On this grant we are exploring how these processes of linguistic evolution might drive the evolution of complexity in humans languages – under what conditions is complexity favoured by the cycle of learning and use by which languages persist?
We are adopting two main approaches to this problem. Firstly, the right kind of complexity in the right place in a linguistic system might facilitate language learning: if so, complexity would be predicted to emerge as a result of the transmission of language from learner to learner over long timescales. Secondly, complex social environments might drive the evolution of expressive power and complexity in language – communication in between cognitively sophisticated individuals who reason about their interlocutors’ linguistic knowledge, world knowledge, and social status, and adjust their linguistic behaviour accordingly, might provide a rich environment in which linguistic complexity can accrue.
These ideas are of far-reaching importance for our understanding of the evolution of language and linguistic complexity, but have not yet been subjected to a concerted empirical examination: our aim in this project is to provide such an examination.
Looking at the impact of complexity on language learning, we have found that factors which are widely claimed to effect the learnability of linguistic systems (including the predictive complexity of morphological paradigms and the extent to which multiple elements of semantics are loaded onto single morphemes) have at most subtle effects on learning in controlled experiments and simulation models, but adults and children show surprising differences in their propensity to use redundant cues of different types. Looking at the impact of social complexity on linguistic complexity, we have conducted a raft of experimental and modelling work showing how human participants adapt to the (inferred) linguistic knowledge of the people they speak to, and used computational models to show how the consequences of those moment-to-moment interactions filter out to reshape the language of whole populations.