[va-richmond-general] article on Starling Songs from the NY Times
- From: "Kathy Kreutzer" <k-kreutzer@xxxxxxxxxxx>
- To: "Va-Richmond-General@Freelists. Org" <va-richmond-general@xxxxxxxxxxxxx>
- Date: Wed, 3 May 2006 13:52:01 -0400
Kathy Kreutzer
Chesterfield, VA
May 2, 2006
Starlings' Listening Skills May Shed Light on Language Evolution
By CARL ZIMMER
The warbles and rattles of a starling seem innocuous enough. But
starlings are now the object of a fierce debate about the nature of
language.
In the current issue of Nature, scientists report that starlings
recognize song patterns based on rules of the sort that make language
possible. Their paper has drawn sharp reactions pro and con from
linguists and animal communication experts.
The debate is over what, if anything, the results mean for human
language. Some scientists believe that the findings offer new clues to
how it evolved. Others dismiss the notion.
Human language is unique in the world of animal communication. Humans
can convey an infinite range of ideas with a limited vocabulary, because
they are not limited to strings of disconnected sounds. Humans can
generate meaning by combining words in various ways, building them into
clauses and inserting those clauses into sentences.
It is possible to come up with all sorts of rules for stringing symbols
together. In the 1950's, Noam Chomsky of the Massachusetts Institute of
Teachnology ranked classes of rules by their power. A very simple rule
might call for one word always to be followed by another word.
Dr. Chomsky argued that the rules that govern language must be more
powerful. At the very least, they must let people embed smaller groups
of words in larger ones again and again - a process sometimes called
recursion.
In 2002, Dr. Chomsky, with Marc D. Hauser of Harvard and W. Tecumseh
Fitch of the University of St. Andrews in Scotland, wrote a paper about
what all this meant for the evolution of language. Language evolution is
vexing, they argued, because it relies on so many things that are not
specific to language.
"Memory is critical to language, because if you couldn't keep in mind
several pieces of a sentence, you couldn't understand anything," Dr.
Hauser said in an interview. "But memory's not specific to language."
Whether any feature was unique to language and to humans remained an
open question. In their paper, Dr. Hauser and his colleagues suggested
that only one thing might fit this bill: the ability to link words and
meaning with the help of recursion.
To test this claim, Dr. Hauser and Dr. Fitch created simple artificial
languages. The words in the languages were made up of two categories of
words. In one category were short sounds made by men, such as "mo" and
"li." The other category were the same sounds made by women. The
difference in the pitch of their voices made it easy to tell words from
the two categories apart.
Dr. Fitch and Dr. Hauser then combined these sounds according to two
different rules. One was a simple rule that a female sound should always
be followed by a male sound.
Then they built sentences with a more complex rule that embedded a
female-male sound pair within another pair. Let A and B stand for the
two kinds of words. The simple rule produces sentences such as ABAB. The
complex rule produces AABB.
As the scientists reported in a 2004 paper, humans figured out both
patterns. College students listen to 30 sentences and then were tested
on new ones. More than 80 percent could correctly say whether a sentence
matched the pattern.
The scientists then tested cotton-top tamarin monkeys. In the evening,
they played recordings of one kind of the pattern to the tamarins. The
next morning they tested the monkeys, noting when the tamarins looked
toward a speaker that played sentences that violated the patterns. The
tamarins noticed when the simple ABAB rule was violated. But they failed
to recognize patterns with the complex AABB rule.
Dr. Fitch and Dr. Hauser concluded that there was a ceiling on the
ability of tamarins to recognize patterns in sounds. But they hesitated
to draw broad conclusions, calling instead for tests on other animals.
Enter the starlings.
The songs of male starlings are made up of warbles, rattles, whistles
and other sounds, collectively known as motifs. "They learn new motifs
and embed them in their songs," said Timothy Gentner, a
neurophysiologist at the University of California, San Diego. Starlings
can also recognize other individuals by learning the unique motifs used
by each bird.
These skills, Dr. Gentner decided, made starlings a perfect choice for
an experiment. He teamed up with three psychologists from the University
of Chicago to see which patterns the birds could recognize.
"We said, 'Well, if there's any species that's capable of doing this,
it's starlings,' " Dr. Gentner said.
Dr. Gentner and his colleagues built an artificial language from warbles
and rattles. They constructed some songs according to the simple ABAB
rule and others according to the complex AABB rule.
The starlings trained by listening to songs. They had to peck at a hole
if a song had the right pattern, and do nothing if it did not. If they
chose correctly, the birds got food; if they chose wrong, the lights
went out briefly.
It took as many as 40,000 trials, but 9 of 11 starlings learned to
recognize the complex AABB pattern over 90 percent of the time. They
could even recognize it when three pairs of warbles and rattles were
inserted between an original pair of warbles and rattles.
"They can do this, and they do it with a high degree of proficiency,"
Dr. Gentner said.
He is confident that he can rule out the possibility that they are using
a very simple strategy, like paying attention to whether a warble was
followed by another warble. If that were true, the birds would react the
same way to an AABB pattern and to AAABB, which violates the rule.
"I was surprised by how well they did when we threw really hard
challenges at them," Dr. Gentner said.
Gary Marcus, a New York University psychologist who wrote a commentary
on the research for Nature, praised it highly. "I thought it was a cool
paper," he said. "The interest here isn't that it's the only species to
do this, but rather that it's the first. It opens the door to see how
widespread this ability is."
It will be important to see if tamarins or other primates can pass the
test with training, Dr. Marcus said. It might turn out that this
ingredient for language already existed in our distant ancestors. The
evolution of language might be "a reconfiguration of old parts," Dr.
Marcus said. "So studies like this show us what those old parts might
be."
Some linguists strongly disagree. "I'm not buying it," said Geoffrey
Pullum, a linguist at the University of California, Santa Cruz, and
co-author of The Cambridge Grammar of the English Language.
For one thing, he said he doubted that the rules the scientists used to
build songs had much to do with the important features of human
language. Dr. Pullum also argued that the tamarin and starling
experiments used "sentences" that were too short and simple to detect
any thought process involved in grammar.
"It's purely about bird abilities, I think, and not about the
foundations of human abilities," he said.
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.
Dr. Hauser added: "This shows a capacity that goes way beyond what we
showed with tamarins. That's what makes it an important paper."
He is intrigued that starlings can recognize patterns even though the
new patterns create no new meaning. "It's still, 'I'm Fred, I'm a male,'
" he said. In humans, this pattern recognition is linked not just to
speech, but to meaning.
Dr. Gentner said, "It's that interface between meaning and pattern where
we humans really excel."
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