Avian race anything but birdbrains, scientists find
Cognitive behavior rivals even chimps, recent studies show
David Perlman, Chronicle Science Editor
Monday, February 7, 2005
Parrots can chat with humans, pigeons can tell a Picasso painting from a Monet and, in the Galapagos islands, Darwin's finches can spear insects with tools they make from cactus spines -- but, contrary to what scientists have long believed, none of them is acting merely on blind instinct or unconscious responses to training.
What those birds are doing, instead, is being smart -- displaying "complex cognitive behavior" as modern brain researchers call it. The new understanding comes from a recent series of experiments and comparative studies of the brain structures of birds, humans and other mammals.
So branding slow-witted people as "birdbrains" is merely ignoring reality, says a group of the world's leading neuroscientists who study the brain circuitry of birds, fish and mammals and who propose that it's high time to abandon old words to describe the brain and adopt a new and better account of brain evolution.
"Evolution has created more than one way to generate complex behavior -- the mammal way and the bird way, and they're comparable to one another," said Erich Jarvis, a Duke University neurobiologist. "In fact, some birds have evolved cognitive abilities that are far more complex than many mammals."
Jarvis heads an international consortium of scientists who have worked for more than seven years studying the brains of birds, fish and mammals. They have published a report on their conclusions in the February issue of the journal Nature Reviews Neuroscience.
Take the striking example of a species of crows in the New Caledonian islands of the South Pacific that has been observed in the wild stripping twigs to make barbed, hooked tools for catching worms.
In experiments by Alex Weir and his colleagues at Oxford University, a captive New Caledonian crow named Betty was frustrated when she couldn't use a bit of straight wire -- which she'd never seen before the start of the experiment -- to snag food from a tiny bucket. Pausing for an instant after an unsuccessful try, she took the wire, bent it around the edge of the food tub, and then snagged the bucket handle with the hook she had fashioned herself.
(If you want the proof, a Quicktime movie of Betty in action is on the Web at:
www.sciencemag.org/feature/data/crow/.) Chimpanzees poke sticks into termite mounds for dinner, but none has ever been known to make even a simple tool -- like straightening a bent piece of pipe in order to reach an apple through a hole -- without being carefully coached by humans, Weir said. The lowly crow shows far more advanced "cognitive behavior" than chimps, the closest genetic relatives of humans, according to Weir and Jarvis' colleagues.
Ever since Darwin, traditional brain researchers have assumed that brain evolution proceeded in step-wise fashion -- "progressive and unilinear," as Jarvis puts it -- from fish, to amphibians, to reptiles, to birds, to primates like monkeys and chimpanzees, and finally to humans.
Thus, it was assumed that only the brains of the "highest" animals like chimps and humans had the cognitive ability to think and learn. That ability was assumed to lie in specific layers of brain cells inside the cerebral cortex. Birds -- having no similar cortex -- were believed to act only through instinct, which is governed by cells in the brain's basal ganglia.
Now, however, modern brain researchers have discovered that bird brains have large clusters of nerve cells occupying space in the brain called the pallium, and that these cell clusters are equally responsible for reasoning, learning and concentrating.
The links between the brain evolution of birds and mammals have resulted from sophisticated new studies in brain imaging, genetic analysis and laboratory experiments tracing the pathways of the central nervous systems in the two widely separated animal groups, according to the findings of the international consortium.
"We have to get rid of the idea that mammals -- and humans in particular -- are the pinnacle of evolution. We also have to understand that evolution is not linear, but an intricate branching process," Jarvis says. "We can't automatically expect to track a structure in the human brain back to other current vertebrate species."
These researchers are not quarreling with Charles Darwin's original concepts of evolution, nor are they breaking with evolution's basic tenets -- that species evolve under the pressures of natural selection.
But they do propose to modify the concept, so that the emergence of intelligent thinking birds and their brains at least take their rightful place alongside the world's mammals and are not relegated to the role of dumb creatures, all instinct and no intelligence.
The nasty word "birdbrain," in the group's thinking, is an arrogant, human-coined insult to an avian race that evolved more than 50 million years after mammals first crept, crawled and stood on the world's stage -- and to the bird brains, which have apparently been evolving even more rapidly than mammalian brains ever since.
The team of 29 neuroscientists from leading research centers in seven nations call themselves the "ThinkTankers" -- or, more formally, as "The Avian Brain Nomenclature Consortium."
In their studies of the brain anatomy of birds and mammals, Jarvis and his colleagues have found many similarities that have long been unrecognized. In the cortex of the human brain, for example, there are six different layers of cells that control functions like speech, learning and concentration. And while songbirds have no such distinct layers, their brains do hold separate clusters of cells that perform "complex cognitive behavior."
Pigeon brains, for example, are endowed with such cell clusters, and the birds are great learners, as a team of Japanese experimenters has found.
The Japanese psychologists found that they could teach pigeons to discriminate between the abstract paintings of Picasso and the impressionistic works of Monet. In several tests the pigeons learned to recognize the difference between the jazzy jumble of Picasso's famed "Three Musicians" and Monet's far more realistic painting "Lady With a Parasol." They could even tell when an image of the Monet painting was shown to them upside-down -- but it was all the same to them when they looked at an upside-down copy of Picasso's work, the researchers noted.
At the University of Arizona, Irene Pepperberg has found that parrots are exceptionally good learners and can even carry on a conversation, although it's limited. Working with an African grey parrot named Alex for more than 20 years, Pepperberg has taught him to count objects, to name their colors even when the object isn't there -- like telling Pepperberg that corn is "yellow" when she merely asks him, and even ordering her around like telling her he wants to "go back" when he's tired.
Barn owls, which have exceptionally good hearing, are excellent at learning from experience. As youngsters they learn to locate their prey at night by homing in on sounds, using their two ears to focus as if they were 3- D cameras -- making what Eric Knudsen, a Stanford neurobiologist, calls an "auditory space map." Even if one ear is plugged, Knudsen's experiments have shown, a barn owl will learn to zero in on its prey after only a few weeks of trial and error on its own..
The detailed proposal for a new lexicon of brain terminology, together with links to laboratory research on the evolution of avian brain structure and capacity, is on the Web at avianbrain.org.