There is a huge amount of linguistic diversity in the world. Isolation and drift due to cultural evolution can explain much of this, but there are many cases where interacting groups use several languages. In fact, by some estimates, bilingualism is the norm for most societies. If one views language as a tool for communicating about objects and events, it seems strange that linguistic diversity should be maintained over time for two reasons. First, it seems more efficient, during language use, to have a one-to-one mapping between signals and meanings. In fact, mutual exclusivity is exhibited by young children and has been argued to be an innate bias and crucial to the evolution of a linguistic system. How or why do bilinguals over-ride this bias? Secondly, learning two language systems must be more difficult than learning one. What is the motivation for expending extra effort on learning an apparently redundant system?
Despite these obstacles, stable bilingualism exists in many parts of the world. How might these arise and be maintained? Nettle (1999) explains the maintenance of many varieties in Papua New Guinea in the following way: The richness of the land means that trading physical commodities is redundant. However, groups still need to co-operate for politics and war. Instead of investing materially, they invest culturally by learning the other communities’ language. It's common for communities to send children to other communities to learn their language. There are even cases of communities consciously agreeing to introduce variation in order to distinguish themselves from other communities. Linguistic diversity, then, becomes a commodity which is maintained.
Crucially, diversity is maintained because the linguistic system has come to encode the speaker’s identity. That is, words refer to properties of the speaker as well as the objects they pick out in the world. In this way, the function of a language in a bilingual context may be radically different from a language in a monolingual context.
Roberts (2010) (Gareth Roberts, henceforth GR) has already described a process through which linguistic diversity can emerge (see my previous post). This was based on the language evolving to encode in-group and out-group identity in a competitive task. The current project looks at how linguistic diversity may arise and be maintained in a co-operative setting. Similarly to GR, this project hypothesises that social structure is key to this emergence. However, there are some differences:
The hypothesis is that linguistic variation can arise due to an accommodation pressure in a specific kind of social network. First, the social network must be sparse - individuals interact mainly within clusters, but there are also some interactions between clusters. Crucially, individuals between groups do not have access to the full interaction history of all their interlocutors. Secondly, the pressure to invest culturally in another group leads to a bias to accommodate another speaker's linguistic system.
This differs in two ways from GR. Firstly, the variation arises in response to a co-operative pressure, rather than a competitive pressure. Secondly, the co-operative nature of the accommodation means that the learners must learn to understand and use multiple varieties, rather than simply distinguishing between 'our' variety and 'other'. It is this difference that could lead to stable, balanced multilingualism rather than many monolingual clusters.
An experiment proposal
Nettle's hypothesis about stable variation could be tested by extending GR's paradigm. GR's experiment was a game where teams of individuals had to trade commodities. Individuals could interact by sending messages to each other in an 'alien' language they learned prior to playing the game. Although all participants were initially given the same starting language, over the course of the game each group developed its own `variety', and this was used as a marker of group identity. Thus, linguistic variation arose due to the linguistic system evolving to encode the identity of the speakers.
This experiment could be extended by placing it in a marketplace environment. Imagine a communal marketplace where sellers compete against each other to sell commodities to customers. In an economy where the differences in quality and cost are negligible, there is a pressure on the seller to attract custom through other means. These include branding, customer loyalty, discounts and so on. If linguistic interactions play a part in the economic transactions (agreeing what to trade, bartering for price etc.), then there is a pressure for the seller to accommodate the customer's linguistic system (i.e. to exhibit greater flexibility). A customer may be more ready to trade with someone who speaks their `language', both for practical reasons (basic comprehension) and social reasons (customer loyalty, honouring agreements).
I predict that, given variation in the customer's speech (generated by drift because of isolation or through GR's in-group/out-group dynamic), a bilingual community of sellers will arise. That is, the linguistic system will come to encode important information about a speaker's identity and also come to be a functional part of the economic system. As Nettle (1999) puts it, speakers will invest culturally in other communities. Given changes to the social structure of the communities, bilingualism may become a stable feature of the society.
However, actually running the experiment is another thing altogether. Maybe I'll have time in the summer ...
Roberts, G. (2010). An experimental study of social selection and frequency of interaction in linguistic diversity Interaction Studies, 11 (1), 138-159 DOI: 10.1075/is.11.1.06rob