Language takes an astonishing variety of forms across the
world—to such a huge extent that a long-standing debate rages around the
question of whether all languages have even a single property in
common. Well, there’s a new candidate for the elusive title of “language
universal” according to a paper in this week’s issue of PNAS.
All languages, the authors say, self-organise in such a way that related
concepts stay as close together as possible within a sentence, making
it easier to piece together the overall meaning.
Language universals are a big deal because they shed light
on heavy questions about human cognition. The most famous proponent of
the idea of language universals is Noam Chomsky, who suggested a
“universal grammar” that underlies all languages. Finding a property
that occurs in every single language would suggest that some element of
language is genetically predetermined and perhaps that there is specific
brain architecture dedicated to language.
However, other researchers argue
that there are vanishingly few candidates for a true language
universal. They say that there is enormous diversity at every possible
level of linguistic structure from the sentence right down to the
individual sounds we make with our mouths (that’s without including sign
languages).
There are widespread tendencies across languages, they concede, but
they argue that these patterns are just a signal that languages find
common solutions to common problems. Without finding a true universal,
it’s difficult to make the case that language is a specific cognitive
package rather than a more general result of the remarkable capabilities
of the human brain.
Self-organising systems
A lot has been written about a tendency in languages to
place words with a close syntactic relationship as closely together as
possible. Richard Futrell, Kyle Mahowald, and Edward Gibson at MIT were
interested in whether all languages might use this as a technique to
make sentences easier to understand.
The idea is that when sentences bundle related concepts in
proximity, it puts less of a strain on working memory. For example,
adjectives (like “old”) belong with the nouns that they modify (like
“lady”), so it’s easier to understand the whole concept of “old lady” if
the words appear close together in a sentence.
You can see this effect by deciding which of these two sentences is easier to understand: “John threw out the old trash sitting in the kitchen,” or “John threw the old trash sitting in the kitchen out.”
To many English speakers, the second sentence will sound strange—we’re
inclined to keep the words “threw” and “out” as close together as we
can. This process of limiting distance between related words is called
dependency length minimisation, or DLM.
Do languages develop grammars that force speakers to neatly package
concepts together, making sentences easier to follow? Or, when we look
at a variety of languages, do we find that not all of them follow the
same pattern?
The researchers wanted to look at language as it’s actually
used rather than make up sentences themselves, so they gathered
databases of language examples from 37 different languages. Each
sentence in the database was given a score based on the degree of DLM it
showed: those sentences where conceptually related words were far apart
in the sentence had high scores, and those where related words sat
snugly together had low scores.
Then, the researchers compared these scores to a baseline.
They took the words in each sentence and scrambled them so that related
words had random distances between them. If DLM wasn’t playing a role in
developing grammars, they argued, we should be seeing random patterns
like these in language: related words should be able to have any amount
of distance between them. If DLM is important, then the scores of real
sentences should be significantly lower than the random sentences.
They found what they expected: “All languages have average
dependency lengths shorter than the random baseline,” they write. This
was especially true for longer sentences, which makes sense—there isn’t
as much difference between “John threw out the trash,” and “John threw the trash out” as there is between the longer examples given above.
They also found that some languages display DLM more than
others. Those languages that don’t rely just on word order to
communicate the relationships between words tended to have higher
scores. Languages like German and Japanese have markings on nouns that
convey the role each noun plays within the sentence, allowing them to
have freer word order than English. The researchers suggest that the
markings in these languages contribute to memory and understanding,
making DLM slightly less important. However, even these languages had
scores lower than the random baseline.
The family tree
This research adds an important piece of the puzzle to the
overall picture, says Jennifer Culbertson, who researches evolutionary
linguistics at the University of Edinburgh. It’s “an important source of
evidence for a long-standing hypothesis about how word order is
determined across the world’s languages,” she told Ars Technica.
Although the paper only looked at 37 languages, it’s
actually incredibly difficult to build these databases of language in
use, which makes it a reasonably impressive sample, she said. There is a
problem here, though: many of the languages studied are related to one
another, representing only a few of the huge number of language
families, so we’d expect them to behave in similar ways. More research
is going to be needed to control for language relatedness.
This paper joins a lot of previous work on the topic, so
it’s not the lone evidence of DLM—it’s corroborating, and adding to, a
fair bit of past research. It’s “a lot of good converging evidence,” she
said.
“There are many proposed universal properties of language,
but basically all of them are controversial,” she explained. But it’s
plausible, she added, that DLM—or something like it—could be a promising
candidate for a universal cognitive mechanism that affects how
languages are structured.
For a debate as sticky as the one about language universals,
there could be multiple ways of interpreting this evidence. Proponents
of Chomsky's school might argue that it's evidence for a dedicated
language module, but those who favour a different interpretation could
suggest that working memory affects all brain functions, not just
language.
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