The cognitive and interactional causes of regularity in language

Why are humans special? Are we special because of our biology, or our capacity to learn from one another, or both? We address this fundamental question by studying the relationship between language universals, language learning, and language transmission.

The languages of the world are superficially rather different: they employ different sounds and build complex utterances in different ways. However, all languages seem to share a common set of structural properties or design features. Where do these language universals come from? One influential hypothesis has suggested that they are a direct reflection of a highly-constraining blueprint for language, which children impose on language during language learning. An alternative possibility is that these properties might be due to weaker biases in learners, which have a very small impact for a particular child learning a particular language, but have a strong effect as a result of the transmission of language over thousands of such episodes of language learning.

Linguistic variation has become a test-case for such questions. Languages exhibit variation: for instance, in English the precise way in which we pronounce the plural marker -s varies (e.g. sometimes "s", as in the plural "cats", sometimes "z", as in "dogs"). However, while it seems logically possible that this kind of variation could occur completely at random (e.g. speakers could randomly chose to use either "s" or "z" - so-called free variation), this type of behaviour very rarely (possibly never) occurs in human languages. Instead, linguistic variation is predictable (in the case of -s, the pronunciation is predictable from the last sound in the noun) i.e. predictable variation is a design feature of language. But why does language work like this?

Some experiments seem to support the hypothesis that the lack of free variation in language is due to strong biases which children impose on language: children don't expect unpredictable variation, and therefore ignore or eliminate it during learning. These experiments use a methodology known as artificial language learning in which children and adults learn miniature languages (created by the experimenter) and are then tested to see whether they change aspects of the language when they use it themselves. Our own work using this same methodology suggests that the differences between children and adult learners may not be as clear cut as earlier work suggested. One of the objectives of the current project is to conduct further learning experiments in order to better understand this difference between adults and child learners, and the extent to which a single learner of any age can re-shape an input language.

This first strand of research therefore studies how *individual* learners respond to unpredictable languages. However, as discussed above, the predictability of natural languages could be a consequence of very weak preferences in individual language learning and use, which accumulate over multiple generations. We will therefore run a second strand of experiments, using only adult participants, where people learn an unpredictable language, use it to communicate with a partner, and then transmit their language to other learners in a diffusion chain (an experimental equivalent to the parlour game "Chinese whispers", where language passes from person to person and potentially changes as it goes). These experiments, together with accompanying computational modelling, will allow us to simulate, in a very simple way, the transmission and use of language in a population.

By combining both strands, we can begin to address the fundamental questions we outlined above: are the universal features of language necessarily due to strong restrictions on language design imposed by child learners, or can far weaker biases inherent in the processes of learning, transmission and use have strong effects on the structure of human language?

This project has important implications for our understanding of the relationship between properties of individual learners and the universal properties of human language and, more broadly, may have implications for our understanding of the relationship between biology and culture in other systems of behaviour. As well as its relevance to academic communities (see section on Academic Beneficiaries), it therefore speaks directly to questions which are of perennial interest to the broader public: why are humans special, and are we special because of our biology, or our capacity to learn from one another, or both? As detailed in the Pathways to Impact document, we will exploit existing networks and expertise to communicate relevant insights and findings from the proposed research to the general public.

In addition to these 'big picture' questions, the way in which children respond to variable input is of specific relevance to parents raising their children in a bilingual family, in particular families where one or both parents are non-native speakers of a language used in the family. In such situations, parents are aware that their non-native language use presents the children with variable input which differs from that provided by the native parent (cf. the case for support for a discussion of the extreme case of Simon, a deaf child of hearing parents who received *only* non-native sign input), which is often a cause for concern. Our reading of the current literature suggests that this concern is probably unwarranted, given the capacity of children to sharpen partially-regular systems, and Exps 1-6 (Exp 6 in particular) will provide further insight on this issue. A colleague at Edinburgh, Prof. Antonella Sorace is the founding director of Bilingualism Matters, a service that disseminates information about the facts and benefits of bilingualism to parents and schools via the web (www.bilingualism-matters.org.uk), an email advice service, public events for children, parents, teachers, educators and employers, and the media. In addition to advising on the implementation of Exp 6, Prof. Sorace will assist us in accessing her existing network of contacts to disseminate relevant findings to such communities.