Universal blues

I have written a news story and a leader for Nature on a new paper examining the notion that there are universal grammatical principles in language. Here they are, in that order. But I must say that, much as the results reported by Dunn et al. chime with my instinctive resistance to universal theories of anything, the comments I’ve received on the paper make me a little sceptical that it does what it claims. Time will tell, I suppose.
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Linguists debate whether languages share universal grammatical features.

Languages evolve in their own idiosyncratic fashion, rather than being governed by universal rules. That’s the conclusion of a new study which compares the grammar of several hundred languages in the light of their evolutionary trees.

Psychologist Russell Gray of the University of Auckland in New Zealand and his coworkers examine the relationships between traits such as the ordering of verbs and nouns in four families representing more than 2,000 languages, and find no sign of any persistent, universal guiding principles [1].

It’s already proving to be a controversial claim. “There is nothing in the paper that brings into question the views that they are arguing against”, says linguist Matthew Dryer of the State University of New York at Buffalo.

There is thought to be around 7,000 languages in the world, which show tremendous diversity in structure. Some have complex ways of making composite words (such as Finnish), others have simple, short and invariant words (such as Mandarin Chinese). Some put verbs first in a sentence, others in the middle and others at the end.

But many linguists suspect there be some universal logic behind this bewildering variety – common cognitive factors that underpin grammatical structures. Two of the most prominent ‘universalist’ theories of language have been proposed by American linguists Noam Chomsky and Joseph Greenberg.

Chomsky tried to account for the astonishing rapidity with which children assimilate complicated and subtle grammatical rules by supposing that we are all born with an innate capacity for language, presumably housed in brain modules specialized for language. He suggested that this makes children able to generalize the grammatical principles of their native tongue from a small set of ‘generative rules’.

Chomsky supposed that languages change and evolve when children reset the parameters of these rules. A single change should induce switches in several related traits in the language.

Greenberg took a more empirical approach, enumerating many observed shared traits between languages. Many of these concerned word order. For example, a conditional clause normally precedes its conclusion: “if he’s right, he’ll be famous.” Greenberg argued that these universals reflect fundamental biases, probably for cognitive reasons. “The Greenbergian word order universals have the strongest claim to empirical validity of any universalist claim about language”, says Gray’s coauthor Michael Dunn of the Max Planck Institute for Psycholinguistics at Nijmegen.

Both of these ideas have implications for the family tree of language evolution. In Chomsky’s case, as languages evolve, certain features should co-vary because they are products of the same underlying parameter. Greenberg’s idea also implies co-dependencies between certain grammatical features of a language but not others. For example, the word order for verb-subject pairs shouldn’t depend on that for object-verb pairs.

To test these predictions, Gray and colleagues used the methods of phylogenetic analysis developed for evolutionary biology to reconstruct four family trees representative of more than 2,000 languages: Austronesian, Indo-European, Bantu and Uto-Aztecan. For each family they looked at eight word-order features and used statistical methods to calculate the changes that each pair of features had evolved independently or in a correlated way. This allowed them to deduce the webs of co-dependence among the features and compare them to what the theories of Chomsky and Greenberg predict.

They found that neither of these two models matched the evidence. Not only do the co-dependencies differ from those expected from Greenberg’s word-order ‘universals’, but they are different for each family. In other words, the deep grammatical structure of each family is different from that of each of the others: each family has evolved its own rules, so there is no reason to suppose that these are governed by universal cognitive factors.

What’s more, even when a particular co-dependency of traits was shared by two families, the researchers could show that it came about in different ways for each – that the commonality may be coincidental. They conclude that the languages – at least in their word-order grammar – have been shaped in culture-specific ways and not by universals.

Other experts express some skepticism about the new results, albeit for rather different reasons. Martin Haspelmath at the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany, says he agrees with the conclusions but that “for specialists they are nothing new”. “It’s long been known that grammatical properties and dependencies are lineage-specific”, he says.

Meanwhile, Dryer, who has previously presented evidence that supports Greenberg’s position, is not persuaded that the results make a convincing case. “There are over a hundred language families that the authors ignore but which provide strong support for the views they are arguing against”, he says. There is no reason to expect a consistent pattern of word-order relationships within families, he adds, regardless of whether they are shaped by universal constraints.

Haspelmath feels it may be more valuable to look for what languages share in common than how they (inevitably) differ. Even if cultural evolution is the primary factor in shaping them, he says, “it would be very hard to deny that cognitive biases play no role at all.”

“Comparative linguists have focused on the universals and cognitive explanations because they wanted to explain something”, he adds. “Saying that cultural evolution is at play basically means that we can’t explain why languages are the way they are – which is largely true, but it’s not the whole truth.”

1. Dunn, M., Greenhill, S. J., Levinson, S. C & Gray, R. D. Nature 10.1038/nature089923 (2011).
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A search for universals has characterized the scientific enterprise at least since Aristotle. In some ways, this quest for common principles underlying the diversity of the universe defines science: without it there is no order and pattern, but merely as many explanations as there are things in the world. Newton’s laws of motion, the oxygen theory of combustion and Darwinian evolution each united a host of different phenomena in a single explicatory framework.

One view takes this impulse for unification to its extreme: to find a Theory of Everything that offers a single generative equation for all we see. It is becoming ever less clear, however, that such a theory – if it exists – can be considered a simplification, given the proliferation of dimensions and universes it might entail. Nonetheless, unification of sorts remains a major goal.

This tendency in the natural sciences has long been evident in the social sciences too. Darwinism seems to offer justification: if all humans share common origins, it seems reasonable to suppose that cultural diversity must also be traceable to more constrained origins. Just as the bewildering variety of courtship rituals might all be considered forms of sexual selection, so perhaps the world’s languages, music, social and religious customs and even history could be governed by universal features. Filtering out what is contingent and unique from what is shared in common might enable us to understand how complex cultural behaviours arose and what ultimately guides them in evolutionary or cognitive terms.

That, at least, is the hope. But a comparative study of linguistic traits by Dunn et al. (online publication doi:10.1038/nature09923) supplies a sharp reality check on efforts to find universality in the global spectrum of languages. The most famous of these was initiated by Noam Chomsky, who postulated that humans are born with an innate language-acquisition capacity – a brain module or modules specialized for language – that dictates a universal grammar. Just a few generative rules are then sufficient to unfold the entire fundamental structure of a language, which is why children can learn it so quickly. Languages would diversify through changes to the ‘parameter settings’ of the generative rules.

In contrast, Joseph Greenberg took a more empirical approach to universality, identifying a long list of traits (particularly in word order) shared by many languages, which are considered to represent biases that result from cognitive constraints. Chomsky’s and Greenberg’s are not by any means the only theories on the table for how languages evolve, but they make the strongest predictions about universals. Dunn et al. have put them to the test by using phylogenetic methods to examine the four family trees that between them represent over 2,000 languages. A generative grammar should show patterns of language change that are independent of the family tree or the pathway tracked through it, while Greenbergian universality predicts strong co-dependencies between particular types of word-order relations (and not others). Neither of these patterns is borne out by the analysis, suggesting that the structures of the languages are lineage-specific and not governed by universals.

This doesn’t mean that cognitive constraints are irrelevant, nor that there are no other universals dictated by communication efficiency. It’s surely inevitable that cognition sets limits on, say, word length or the total number of phonemes. But such ‘universals’ seem likely to be relatively trivial features of languages, just as may be the case for putative universals in music and other aspects of culture. We should perhaps learn the lesson of Darwinism: a ‘universal’ mechanism of adaptation says little of interest, in itself, about how a particular feature got to be the way it is, or how it works. This truth has dawned on physicists too: universal equations are all very well, but particular solutions are what the world actually consists of, and those particulars are generally the result of contingent history.