Linguistic Diversity and Universal Grammar

One of the most important ideas to come from the Chomsky program of linguistic thought is the idea of universal grammar (aka UG), a "deep" structure of human cognition that is innate and universal to all humans. It is the existence of this UG that allows humans to acquire language in the first place, for it is the UG that guides the young child's interpretation of the language around her.

Neat idea. So, let's go look for it. Avanti!

Over the years, however, as the Chomsky program has acquired critics, UG has been one point of contention. Perhaps the diversity among languages is so very great no UG can plausibly account for it.

But, you might ask, if there is no Universal Grammar then what happens to our vaunted capacity for language? Is it as empty as UG? And, if so, just how DO we learn language, and WHO are we anyhow?

Good questions, Grasshopper, good questions. They're all in play.

Sean Roberts over at Replicated Typo (where I occasionally post) reports a recent debate on the subject. His opening paragraphs:

There was a debate today between Peter Hagoort and Stephen Levinson on ‘The Myth of Linguistic Diversity”.  Hagoort arguing the case for universalist accounts.  He admitted that language does exhibit a large amount of diversity, but that this diversity is constrained.  He argued that linguistics should be interested in which universal mechanisms explain the boundary conditions for linguistic diversity.  The most likely domain in which to find these mechanisms is the brain.  It comes with internal structure that defines the boundary conditions on the surface structures of human behaviours.  These boundary conditions include the learnability of input, and that language is processed incrementally and under time constraints.  Brains operate under these constraints so that linguistic processing of all languages happens in roughly the same processing stages.  Hagoort argued that proponents of a diversity approach to linguistics think that variation is unbounded or constrained only by culture.  While there is variation between individuals and between languages, it is the general types that we should be focussed on.

In contrast, Levinson suggested that we should be moving away from the picture of the modal individual with a fixed language architecture.  Instead, we should embrace population thinking and recognise the variation inherent at every level of language from typology to processing and brain structures.  While languages are constrained by the processing structures of the brain, these processing structures are plastic and adapt to the language and cultures in which they are embedded.  Adults lose the ability to distinguish sounds that are not part of their language.  Recent work on linguistic planning using eye-tracking shows that the elements of a scene that speakers attend to before starting to speak differs with the canonical word order of their language.  More fundamentally, brain structures can be affected by cultural experience, such as bilingualism or singing (indeed, the effect of bilingualism on processing shows that variation itself is a fundamental constraint).  So, brains do constrain learning and processing, but are themselves subject to constraints from interaction between individuals.  Brains also change over evolutionary time, adapting to a range of pressures.  Therefore, there is a complex ecology of systems that co-evolve to define the constraints on language, and understanding these systems requires focussing on diversity.

The take-home:

The general message:  Proponents of universals need to take diversity into account, and proponents of diversity need to be more specific about how diversity maps onto processing and how different domains of language co-evolve.

Sounds to me like we need to rethink the enterprise with a sharper set of questions, categories, and models.

The issue has been hashed out in the pages of Behavioral and Brain Sciences (2009: 32, 429–492). Nicholas Evans and Stephen C. Levinson provided an article, The myth of language universals: Language diversity and its importance for cognitive science (PDF), and 23 others commented. Here's their abstract:

Talk of linguistic universals has given cognitive scientists the impression that languages are all built to a common pattern. In fact, there are vanishingly few universals of language in the direct sense that all languages exhibit them. Instead, diversity can be found at almost every level of linguistic organization. This fundamentally changes the object of enquiry from a cognitive science perspective. This target article summarizes decades of cross-linguistic work by typologists and descriptive linguists, showing just how few and unprofound the universal characteristics of language are, once we honestly confront the diversity offered to us by the world’s 6,000 to 8,000 languages. After surveying the various uses of “universal,” we illustrate the ways languages vary radically in sound, meaning, and syntactic organization, and then we examine in more detail the core grammatical machinery of recursion, constituency, and grammatical relations. Although there are significant recurrent patterns in organization, these are better explained as stable engineering solutions satisfying multiple design constraints, reflecting both cultural-historical factors and the constraints of human cognition.

Linguistic diversity then becomes the crucial datum for cognitive science: we are the only species with a communication system that is fundamentally variable at all levels. Recognizing the true extent of structural diversity in human language opens up exciting new research directions for cognitive scientists, offering thousands of different natural experiments given by different languages, with new opportunities for dialogue with biological paradigms concerned with change and diversity, and confronting us with the extraordinary plasticity of the highest human skills.