Cultural Evolution of Language: Implications for Cognitive Science

Cultural Evolution of Language: Implications for Cognitive Science Moderator: Morten H. Christiansen (christiansen@cornell.edu) Department of Psychology, Cornell University & Santa Fe Institute Nick Chater (n.chater@ucl.ac.uk) Division of Psychology and Language Sciences, University College London Thomas L. Griffiths (tom_griffiths@berkeley.edu) Department of Psychology, University of California, Berkeley Simon Kirby (simon@ling.ed.ac.uk) School of Philosophy, Psychology and Language Sciences, University of Edinburgh Keywords: language evolution; cultural transmission; language acquisition; inductive biases; genetic constraints Introduction The past couple of decades have seen an explosion of research on language evolution, initially fueled by Pinker and Bloom’s (1990) groundbreaking article arguing for the natural selection of biological structures dedicated to language. The new millennium has seen a shift toward explaining language evolution in terms of cultural evolution rather than biological adaptation. Indeed, theoretical and computational considerations indicate that there are substantial restrictions on what linguistic properties can evolve through natural selection (Chater, Reali & Christiansen, 2009; Christiansen & Chater, 2008). In contrast, cultural evolution is now emerging as a key paradigm for understanding the evolution of language. A rapidly growing bulk of work has begun to show how nonlinguistic inductive biases amplified by cultural transmission across generations may help explain many facets of linguistic structure observable in today’s languages (see Brighton, Smith & Kirby, 2005, for a review). The basic insight from this work has been that wherever there is imperfect transmission from one agent to another, the transmission process becomes an adaptive system. Put simply, the inevitable product of cultural transmission is a system of behavior that appears to be designed to optimize transmissibility. In the case of language, computer simulations suggest that many key features of syntactic and phonological structure arise as adaptations to constraints like stimulus poverty, noise, processing constraints, etc. Crucially, this research has many important implications for cognitive science, not only in terms of the nature of the biases to consider in language acquisition but also for cognition, more generally. So far, however, little of this work has surfaced at this conference or in the Cognitive Science journal. In this symposium, we therefore take stock of current work on the cultural evolution of language, highlighting key implications of this work for cognitive scientists from different perspectives, ranging from philosophical considerations (Chater) and Bayesian analyses (Griffiths) to evolutionary psycholinguistics (Kirby) and molecular genetics (Christiansen). The participants in this symposium have all worked extensively on both language evolution and cognitive science, more generally. Chater has been exploring the interaction of language acquisition and evolution, especially using formal analyses. Griffiths has been using mathematical analyses and laboratory experiments to explore how inductive biases influence the outcome of cultural evolution. Kirby has used multi-agent simulation modeling to understand the adaptive dynamics of the cultural transmission of language, and more recently has constructed close analogs of these simulations in laboratory experiments. Christiansen has conducted both agent-based simulations and artificial language learning experiments to explore cultural evolution of linguistic structure, and is currently using molecular genetics to investigate the innate preconditions for the cultural transmission of language. Together, the participants have published nearly 100 papers relating to language evolution, including in high-quality journals such as Behavioral & Brain Sciences, Proceedings of the National Academy of Sciences, Proceedings of the Royal Society, and Trends in Cognitive Sciences. Chater: Cultural Induction and Language Acquisition There are two very different types of inductive inference problems. In induction about the natural world, data is generated by some external source, and the learner attempts to predict how it continues. In cultural induction, by contrast, the objective is to make the same predictions as other learners. Thus, in language acquisition, children receive partial linguistic input, and must generalize to many new linguistic structures—but the standard of correctness is to generalize in the same way as other learners. To the extent that learners have the same biases and prior experience, this dramatically simplifies the learning problem, because their generalizations will typically agree. More generally, language evolution itself can be viewed as the accretion of successive generalizations upon which learners converge. This perspective radically reshapes the