News of advances or challenges in the evolution of speech typically concern just one school of thought. Such was the case with a brouhaha that arose late last spring over the syntactical abilities of starlings. Many linguists believe syntax defines the distinctive nature of language. These syntax firsters were in an uproar. Most other people could only wonder what they excitement was all about. Some birds learned to discriminate between meaningless sounds. Is that relevant to language?
The fuss began with Stephen Pinker’s book The language Instinct (1994). It argued that the brain has modules specifically for organizing words into sentences; however, doubters wondered, are we really supposed to believe that there was a strong selective pressure lasting for many generations that favored proper syntax when even today people regularly misspeak without suffering serious consequences?
Problems like these have forced a revision in ideas about the biology of syntax. Instead of looking for many language-only modules, many linguists, including Noam Chomsky, concentrate on the evolution of the ability to form recursive sentences.
Recursive rules repeat themselves. In a recursive procedure a system follows a rule and then can then follow the rule again. Take, for example, this bit of fundamental news:
A man bit a dog.
We can break that sentence into two parts:
- a noun phrase (a man) and
- a verb phrase (bit a dog).
We can break that verb phrase into two more parts:
- a verb (bit) and
- another noun phrase (a dog).
Recursion is the ability to keep on putting the same structural components (like noun phrases) into a single whole. We can say that sentences may be formed by generating a noun phrase + a verb phrase and we can make more complicated sentences without adding new rules. We can simply expand the verb phrase so that it contains yet another a verb phrase (verb + another noun phrase): A man bit a dog and banged his nose.
You can wonder if the infinitely long sentences that can be produced by such recursion are truly English, but Chomsky insists that recursive syntax is what enables people to utter an endless variety of new sentences and in 20002 he put that position in stone. The journal Science published an article by Marc Hauser, Noam Chomsky and Tecumseh Fitch titled “The Faculty of Language: What Is It, Who Has It, and How Did It Evolve?”(Abstract here.) The article distinguished between the “broad” faculty of language and a more “narrow” faculty.
The broad faculty covers many of the areas required for producing speech sounds, having a meaning to express, and organizing the sounds syntactically. It could have evolved in animals and predates language.
The narrow faculty is the part that is uniquely human. It consists of the ability to generate an infinite number of sentences from a finite set of recursive rules.
The Hauser-Chomsky-Fitch thesis was that this recursive ability is THE one feature of language that is unique to humans. Their article included an experiment in which humans heard examples of meaningless“sentences” generated by two simple sets of rules. One of the rules was recursive, one was not. The human listeners were able to learn both patterns and recognize which rule set was being used. Cotton-top tamarin monkeys, however, did not notice mistakes in the recursive patterns.
The starling test that got so much attention challenged the Hauser-Chomsky-Fitch findings. The research appeared in an article published last April in Nature by Timothy Gentner, Kimberley Fenn, Daniel Margoliash and Howard Nusbaum, “Recursive syntactic pattern learning by songbirds.”
They tried to repeat the Hauser et al experiment by using starlings instead of cotton-top tamarins. It took a great deal of effort, over 12,000 exposures for even the quickest learning birds, but four out of eleven starlings generalized their responses well enough to respond appropriately to new songs generated by recursive rules while ignoring the new songs that did not.
A teenage blogger on MySpace.com asked Chomsky for a comment. Chomsky responded that the training had not involved recursion at all:
... not understanding the elementary mathematics, [the experimenters] concluded that starlings were learning context-free systems, hence on their way to language. Amazingly, an article with such an elementary fallacy made it to "Nature," a serious scientific journal.
Even so, the starling experiment has thrown the syntax-firsters on the defensive. Having surrendered so much ground to the “broad language faculty,” they have bet the bank on a narrow, recursive faculty. Meanwhile, others schools of thought roll untouched by the news. Dr. Gentner, the lead author of the starling paper, told the New York Times (available here($)), ''It's that interface between meaning and pattern where we humans really excel.'' It is how you mix meaning and grammar that makes language so intriguing.