January 26th: Simon Kirby

Cultural evolution creates duality of patterning: the role of population structure in the simplicity/expressivity trade-off

Simon Kirby, University of Edinburgh

Tuesday, Jan 26 2021, 11:00-12:00 GMT
Zoom Details: [Please Request]

One of the core design features of human language is Duality of Patterning, that is languages are organised such that meaningful signals are created out of combinations of meaningless elements (an organisation that can be seen most clearly in the existence of minimal pairs in a language’s lexicon). What are the origins of this structure, and to what extent does its explanation help us understand combinatorial behaviour more widely?

In this work-in-progress talk, I will present preliminary results from a simulation that seeks to answer this question. I will argue that combinatorial structure in signals is the result of a trade-off between a pressure for simplicity arising from learning, and a pressure for expressivity arising from communication. In this way, we can see duality of patterning as yet another aspect of language that is explained by these two forces operating together in cultural evolution.

I will also use this model to explain why there is at least one language – Al-Sayyid Bedouin Sign Language – which does not exhibit duality of patterning, and show that the trade-off between learning and communication can be affected by population structure. Specifically, the degree to which learners (as opposed to adults) contribute input to the data of the next generation of learners alters the balance of forces, promoting or inhibiting the emergence of systematic combinatorial structure.