Can Crows Make Mental Pictures of Tools?New Caledonian crows were trained to seek rewards by tearing paper of a certain size, demonstrating what researchers say is quite advanced toolmaking.
The New York Times by Karen Weintraub
A New Caledonian crow manipulating a paper “tool” in an experiment. Researchers report in a new study that the crows can make simple tools from memory.CreditSarah Jelbert
New Caledonian crows are known for their toolmaking, but Alex Taylor and his colleagues wanted to understand just how advanced they could be.
Crows from New Caledonia, an island in the South Pacific, can break off pieces of a branch to form a hook, using it to pull a grub out of a log, for instance. Once, in captivity, when a New Caledonian male crow had taken all the available hooks, its mate Betty took a straight piece of wire and bent it to make one.
“They are head and shoulders above almost every other avian subjects” at toolmaking, said Irene Pepperberg, an avian cognition expert and research associate in Harvard University’s department of psychology. “These crows are just amazing.”
Dr. Taylor, a researcher at the University of Auckland in New Zealand, and several European colleagues wondered how the crows, without an ability to talk and showing no evidence of mimicry, might learn such sophisticated toolmaking.
Perhaps, the scientists hypothesized in a new paper published Thursday in Scientific Reports, they used “mental template matching,” where they formed an image in their heads of tools they’d seen used by others and then copied it.
“Could they look at a tool and just based on mental image of the tool — can they recreate that tool design?” Dr. Taylor said. “That’s what we set out to test, and that’s what our results show.”
In a series of steps, the researchers taught the birds to feed pieces of paper into a mock vending machine to earn food rewards. The scientists chose a task that was similar enough to something the animals do in the wild — while also brand new. The birds had never seen card stock before, but learned how to rip it into big or little shapes after being shown they would get a reward for the appropriate size.
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The template used to show the birds the right size of paper was not available to them when they made their “tools,” yet the crows were able to use their beaks to tear off bits of paper, which they sometimes held between their feet for leverage.
The finding is consistent with what previous research has shown about the brains of songbirds, said John Marzluff, an expert in crow behavior and a professor of wildlife science at the University of Washington.
Earlier research has shown that connected neural circuits in the front part of the brain allow songbirds to learn songs they heard their parents sing months earlier, and might be useful for other complex activities, he said. “I thought their demonstration of behavior that’s consistent with that in tool manufacturing was really cool,” Dr. Marzluff said.