By James Gorman, The New York Times, December 22, 2011
 |
| Pigeons are used in experiments to gauge their ability to do higher math |
By now, the
intelligence of birds is well known. Alex the African gray parrot had great
verbal skills. Scrub jays, which hide caches of seeds and other food, have
remarkable memories. And New Caledonian crows make and use tools in ways that
would put the average home plumber to shame.
Pigeons, it turns
out, are no slouches either. It was known that they could count. But all sorts
of animals, including bees, can count. Pigeons have now shown that they can
learn abstract rules about numbers, an ability that until now had been
demonstrated only in primates. In the 1990s scientists trained rhesus monkeys
to look at groups of items on a screen and to rank them from the lowest number
of items to the highest.
They learned to
rank groups of one, two and three items in various sizes and shapes. When
tested, they were able to do the task even when unfamiliar numbers of things
were introduced. In other words, having learned that two was more than one and
three more than two, they could also figure out that five was more than two, or
eight more than six.
Damian Scarf, a
postdoctoral fellow at the University of Otago, in New Zealand, tried the same
experiment with pigeons, and he and two colleagues report in the current issue
of the journal Science that the pigeons did just as well as the monkeys.
Elizabeth Brannon,
a professor of psychology and neuroscience at Duke University, and one of the
scientists who did the original experiments with monkeys, was impressed by the
new results. “Their performance looks just like the monkeys’,” she said.
Score one for the
birds. The pigeons had learned an abstract rule: peck images on a screen in
order, lower numbers to higher. It may have taken a year of training, with
different shapes, sizes and colors of items, always in groups of one, two or
three, but all that work paid off when it was time for higher math.
Given groups of six
and nine, they could pick, or peck, the images in the right order. This is one
more bit of evidence of how smart birds really are, and it is intriguing
because the pigeons’ performance was so similar to the monkeys’. “I was
surprised,” Dr. Scarf said.
He and his
colleagues wrote that the common ability to learn rules about numbers is an
example either of different groups — birds and primates, in this case —
evolving these abilities separately, or of both pigeons and primates using an
ability that was already present in their last common ancestor.
That would really
be something, because the common ancestor of pigeons and primates would have
been alive around 300 million years ago, before dinosaurs and mammals. It may
be that counting was already important, but Dr. Scarf said that if he had to
guess, he would lean toward the idea that the numerical ability he tested
evolved separately. “I can definitely see why both monkeys and pigeons could
profit from this ability,” he said.
No testing has been
done with numbers greater than nine, so whether a pigeon can count large
numbers of bread crumbs or popcorn kernels is a question still open to
investigation.
No comments:
Post a Comment