Birds can be grammatically correct
A few months ago, I told you about the gift of a parrot for mathematics. Now, American researchers have proven that humble starlings can learn grammar (read these two news releases -- here and there -- for lots of details). It took a month and some food as a reward to train the birds to recognize 'bird phrases' about 90% of the time. Still one researcher said that the birds don't have the same grammar skill as his 9-month-old boy. But these experiments might revolutionize the field of linguistics. Read more...
Let's start with a picture of one these starlings singing in the woods (Credit: University of Chicago, Daniel Margoliash's lab). You'll find other images on this page and here is a link to a larger version of the bird singing.
Here is the introduction of the University of Chicago Medical Center news release.
Although linguists have argued that certain patterns of language organization are the exclusive province of humans -- perhaps the only uniquely human component of language -- researchers from the University of Chicago and the University of California San Diego have discovered the same capacity to recognize such patterns and distinguish between them in Sturnus vulgaris, the common European starling.
And these starlings have certainly lots of talent.
Although they are not known for the lilting beauty of their songs, starlings produce an amazing array of complex sounds, combining chirps, warbles, trills and whistles with rattling sounds.
They also have a talent for mimicry. One starling famously copied an unpublished tune that Mozart whistled in a pet store; the composer purchased the bird and kept it as a pet. The starling is mentioned only once in all of Shakespeare, but in that passage an angry warrior, forbidden by the King to speak of a rival, Mortimer, decides he will "have a starling shall be taught to speak nothing but 'Mortimer,' and give it him to keep his anger still in motion."
This is one of the reasons Daniel Margoliash, professor of anatomy and organismal biology at the University of Chicago, and Timothy Gentner, assistant professor of psychology at the University of California, San Diego decided to assess the birds' syntactical skills.
Here are some details about their experiments given by the University of California, San Diego news release.
Gentner and his coauthors created artificial starling songs that followed two different patterning rules: a "context-free" rule, which allows for a sound to be inserted in the middle of an acoustic string and is the simplest form of recursive center-embedding; and a "finite-state" rule, of the sort thought to account for all non-human communication, that allows for sounds to be appended only at the beginning or end of a string.
Capitalizing on the diverse range of sounds in starling songs, the researchers used recordings of eight different "warbles" and eight different "rattles" from a single male starling to construct a total of 16 artificial songs. Eight of these songs followed the context-free sequence AnBn (i.e. AABB or rattle-rattle-warble-warble) and eight followed the finite-state (AB)n (i.e. ABAB or rattle-warble-rattle-warble).
Eleven adult birds were then taught to distinguish these two sets of songs using classic reinforcement techniques. The birds were rewarded with food for pecking at a button when they heard a song from the context-free set and for refraining when they heard one from the finite-state set.
Below is a diagram showing how the starlings were trained (Credit: University of California, San Diego, Timothy Gentner's lab).
And was it difficult to train the birds?
Nine of the starlings -- after 10,000 to 50,000 trials over several months -- eventually learned to distinguish the patterns. When tested with different combinations of rattles and warbles that followed the same rules, the starlings performed well above chance, suggesting they had learned the abstract patterns and not just memorized the specific songs.
So what kind of conclusion can we draw from these experiments?
Gentner says, "The more closely we understand what nonhuman animals are capable of, the richer our world becomes. Fifty years ago, it was taboo to even talk about animal cognition. Now, there are Nova specials on the subject and no one doubts that animals have complex and vibrant mental lives. This study is a powerful statement about what even birds can do: Look at what they're learning."
This research work has been published by Nature under the name "Recursive syntactic pattern learning by songbirds" (Volume 440, Number 7088, Pages 1204-1207, April 27, 2006). Here is a link to the editor's summary, "The language of birdsong" which analyses the birds' performances.
Their performance can be said to be almost human on this yardstick. So if there are language processing capabilities that are uniquely human, they may be more context-free or at a higher level in the Chomsky hierarchy. Or perhaps there is no single property or processing capacity that differentiates human language from non-human communication systems.
For more information, here are two links to the abstract of the paper and to some supplementary information (PDF format, 10 pages, 1.31 MB) from which the above diagram has been extracted.
Sources: University of Chicago Medical Center news release, April 26, 2006; University of California, San Diego news release, April 26, 2006; Nature, April 27, 2006; and various web sites
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