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Neo-Caledonian crows have been trained to seek rewards by tearing paper of a certain size, demonstrating what the researchers say is a fairly advanced toolmaking.
Caledonian crows are known for their tools, but Alex Taylor and his colleagues wanted to understand how much they
Crows from New Caledonia, a South Pacific island, can break pieces of branches to form a hook, for example to pull a larva from a log. Once, in captivity, when a male crow of New Caledonia had taken all the hooks available, his mate Betty took a straight wire and folded it to make one.
"They are head and shoulders above almost every other avian subject" Irene Pepperberg, expert on avian cognition and research badociate at the Department of Psychology at Harvard University. "These crows are just unbelievable."
Dr. Taylor, a researcher at the University of Auckland in New Zealand, and several European colleagues wondered how crows, without the ability to speak and showing no evidence of mimicry, could learn such sophisticated tooling .
Hypothesis in a new article published Thursday in the scientific reports, they used "mental matching", where they formed a picture in the head of the tools that they had seen used by d & # 39; others, then copied.
"Could they look at a tool and just based on the mental image of the tool – can they recreate that tool design?" Said Dr. Taylor. "That's what we tried to test, and that's what our results show."
In a series of steps, the researchers taught the birds to feed pieces of paper in a vending machine to earn food rewards. Scientists chose a task that was quite similar to something animals do in the wild – just as new. The birds had never seen cardstock before, but they learned to cut it into large or small shapes after showing that they would receive a reward for the proper size.
The template used to show birds the correct size of paper was not available to them when they were making their "tools", but crows could use their beaks to snatch pieces of paper that they were holding sometimes in their hands. feet for the leverage.
The discovery is consistent with what previous research has shown on the brains of songbirds, said John Marzluff, a raven behavior expert and a professor of wildlife science at the University of Washington .
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Dr. Pepperberg, who once taught a parrot named Alex over 100 English words, said researchers still needed to do more work to prove that crows form mental images of the model.
"This would seem to be the experience of a series of other experiments," she said. "The birds really showed an interesting inference, but they were driven into the garden."
Just before asking the crows to rip the paper in the right size, the researchers showed them exactly what size of paper would bring them a reward. "The fact that they choose to make a small piece of paper, for example, is interesting," said Dr. Pepperberg. "But it would be a lot more interesting if they had not seen it and were rewarded 30 seconds before they did it."
She said that she would find it extremely exciting if this team or another conclusively shows that crows can learn by making a mental picture.
Dr. Marzluff said that there was always more research to be done, but that he was comfortable with the group's conclusions that such a thought is occurring. And, he said, he has never heard of another animal performing such a task.
"The use of tools and the gradual accumulation of skill or complexity in the tools is something that has not been demonstrated to any other species than the humans, "he said, adding that this should teach humans a certain humility. world. "We are not so unique ourselves, just maybe better or more advanced at doing certain tasks."
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