2967. Can Crows Make Mental Pictures of Tools?

By Karen Weintraub, The New York Times, June 28, 2018

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. Photo: Sarah Jelbert.

New Caledonian crows are known for their toolmaking, but Alex Taylor and his colleagues wanted to understand just how advanced they could be 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.

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.

Dr. Pepperberg, who once famously taught a parrot named Alex over 100 English words, said the researchers still needed to do more work to prove that the crows form mental pictures of the template.

“This would seem to be experiment one in a series of other experiments,” she said. “The birds really did show an interesting inference, but they were led down the garden path.”

Just before asking the crows to rip the paper into the right size, the researchers showed them exactly what size paper would earn them a reward. “The fact that they choose to make a small piece of paper, for example, is interesting,” Dr. Pepperberg said. “But it would be a lot more interesting if they hadn’t seen it and been rewarded 30 seconds before they had to do it.”

She said 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 thinking occurs. And, he said, he’s never heard of another animal accomplishing such a task.

“The tool use and the progressive accumulation of proficiency or of complexity in tools is something that hasn’t been demonstrated in species other than humans to my knowledge,” he said, adding that this should teach humans some humility about our own position in the world. “We’re not so unique ourselves. Just perhaps better or more advanced at doing certain tasks.”