Chris at Mixing Memory has a post from last week reflecting on the meaning of the finding that starlings can learn certain patterns of syntactic recursion.
He also links to two message-board posts by linguists on the topic. This one, by Mark Liberman explains why recursion is important and what a Dyck language is:
If you're like every other human I've tested, you find this task pretty hard. If you're quick and you care enough, you can count on your mental fingers, so to speak, adding one for each higher pitch and subtracting one for each lower pitch, and "parse" the sequence that way. But the difference between the Dyck and non-Dyck patterns is not, in the general case, cognitively salient to humans without intellectual scrutiny. In contrast, we don't need to count on our mental fingers to understand the structures of real spoken language. And I'd be astounded if the difference between Dyck and non-Dyck strings is cognitively salient to starlings or to any other animals either.
This post by David Beaver has a practical illustration, and reflects on the study:
Faced with the facts about starlings innate ability to learn Dyck languages, and the facts about center embeddings for you and me, a contrarian might well conclude that yes, at last, we have firm and amazing evidence for a biologically unique language module. The trouble is, starlings have it, and we don't.
And this post at Tenser, said the Tensor is another explanation:
However, this does not imply that the birds are recognizing context-free languages when they're processing the songs. It's true that CFGs are the next step up the Chomsky hierarchy from regular languages, but that's a fact about the hierarchy, not about the universe -- there are other kinds of languages that are supersets of the regular languages while still being subsets of context-free languages. The researchers propose a few of these and show why they're not sufficient to account for the birds' success, but I suspect the birds may be processing one they didn't consider. In particular, the starlings may just be using memory.
It's heavy stuff, but important to the evolution of language, since it reflects on the logical prerequisites for generating and processing linguistic messages.
Meanwhile, before I posted, I found that Carl Zimmer has written about the study for the NY Times. Nice exchange between Gentner, Chomsky and Hauser at the end:
Dr. Chomsky also rejects Dr. Gentner's conclusions. He suggests the starlings are merely counting rattles, storing the number in their memory, then counting warbles. "It has nothing remotely to do with language -- probably just with short-term memory," he said via e-mail. Dr. Gentner argues that even if the starlings are counting, they are still using a strategy more sophisticated than has been seen before in animals.
"Chomsky may find this trivial, but that is a bit like saying apes use tools, but only the trivial kind that lack the sophistication of a tri-square or a laser level," he said.