Do New Caledonian crows solve physical problems through causal reasoning?
My friends working on the New Caledonian Crow have a new paper out in today's Proceedings of the Royal society. The paper "Do New Caledonian crows solve physical problems through causal reasoning?" by Alex Taylor et al provides evidence of how crows can reason about physical problems:
The extent to which animals other than humans can reason about physical problems is contentious. The benchmark test for this ability has been the trap-tube task. We presented New Caledonian crows with a series of two-trap versions of this problem. Three out of six crows solved the initial trap-tube. These crows continued to avoid the trap when the arbitrary features that had previously been associated with successful performances were removed. However, they did not avoid the trap when a hole and a functional trap were in the tube. In contrast to a recent primate study, the three crows then solved a causally equivalent but visually distinct problem—the trap-table task. The performance of the three crows across the four transfers made explanations based on chance, associative learning, visual and tactile generalization, and previous dispositions unlikely. Our findings suggest that New Caledonian crows can solve complex physical problems by reasoning both causally and analogically about causal relations. Causal and analogical reasoning may form the basis of the New Caledonian crow's exceptional tool skills.
We're trying out a new way of presenting results - crowtube! Another friend of ours, Marc Tadaki, has made a (wonderful) video of Alex explaining the experiment:
Mirror self-recognition in Magpies
Frans de Waal in PLoS Biology:
The Eurasian magpie (Pica pica) has a poor reputation. As a child, I learned never to leave small shiny objects, such as teaspoons, unattended outdoors as these raucous birds will steal anything they can put their beaks on. This folklore even inspired a Rossini opera, “La gazza ladra” (“The Thieving Magpie”). Nowadays, this view has been replaced with one that is more sensitive to ecological balance, in which magpies are depicted as murderous plunderers of the nests of innocent songbirds. Either way, they are black-and-white gangsters.
But no one has ever accused a magpie of being stupid. The bird belongs to the Corvidae, a worldwide family (also including crows, ravens, jackdaws, jays, and nutcrackers) marked by an exceptionally large forebrain, which permits innovative foraging. In recent years, this family has begun to pose a challenge to the idea that primates constitute the pinnacle of cognitive evolution by showing creative tool-use, visual perspective-taking, foresight, and so on.
How to think, I think
From Ed Boyden's blog: How to think:
When I applied for my faculty job at the MIT Media Lab, I had to write a teaching statement. One of the things I proposed was to teach a class called "How to Think," which would focus on how to be creative, thoughtful, and powerful in a world where problems are extremely complex, targets are continuously moving, and our brains often seem like nodes of enormous networks that constantly reconfigure. In the process of thinking about this, I composed 10 rules, which I sometimes share with students. I've listed them here, followed by some practical advice on implementation.
Extremely large brains in New Caledonian Crows
Long-term readers will know that I've got a number of friends working on the wonderfully intelligent New Caledonian Crow. These birds make and use a number of different tools for extracting grubs from logs. You can see my catalogue of posts on these birds here.
Recently, they've got a new paper out showing that the brains of these crows is large and more encephalized than other crow species (corvids) and most of the other birds studied. The paper is here: Extraordinary large brains in tool-using New Caledonian crows (Corvus moneduloides), and the abstract says:
A general correlation exists between brain weight and higher cognitive ability in birds and mammals. In birds this relationship is especially evident in corvids. These animals are well-known for their flexible behavior and problem-solving abilities, and have relatively large brains associated with a pallial enlargement.
At the behavioral level, New Caledonian crows stand out amongst corvids because of their impressive object manipulation skills both in the wild and in the laboratory. However, nothing is known about the relative size of their brains.
Here we show that NC crows have highly encephalised brains relative to most other birds that have been studied. We compared the relative brain size of five NC crows with combined data for four passerine species (7 European carrion crows, 2 European magpies, 3 European jays and 4 domestic sparrows) and found that NC crows had significantly larger brains.
A comparison only with the seven carrion crows also revealed significantly larger brains for NC crows. When compared with brain data for 140 avian species from the literature, the NC crow had one of the highest degrees of encephalisation, exceeding that of the 7 other Corvidae in the data set.
Boston Globe: How bird brains are shaking up science
Jonah Lehrer in The Boston Globe:
THE NEW CALEDONIAN crow is surprisingly smart about its food. Its favorite insects live in tiny crevices that are too narrow for its beak. So the crow takes a barbed leaf and, using its beak and claws, fashions a primitive hook. It then lowers the hook down into the cracks, almost like a man fishing, and draws up a rich meal. Some scientists even suggest that crows are more sophisticated tool builders than chimps, since they can transmit their knowledge on to successive generations and improve the tools over time. These birds have a culture.
Meta-tool use in New Caledonian Crows
Everyone thinks that chimpanzees and other primates are good candidates for finding complex cognitive capabilities in non-human animals. Unfortunately, they're just not that smart, really. Sure, they can use sticks to fish termites out of holes, however, there's another animal which can go a bit further.
The New Caledonian Crow (Corvus moneduloides) is known to manufacture a number of different tool types for to extract grubs from rotting logs. For example, they can trim down a twig into a fish-hook shaped device, or they slice off a strip of Pandanus leaf (a flax-like plant) and use the barbs on the leaf as hooks. The actions they go through here are far more complex than anything observed in any other non-human animal, including chimps.
Today, some good friends of mine Alex Taylor, Gavin Hunt, Jenny Holzhaider, and my boss, Russell Gray, have a paper out in Current Biology which shows that these crows can spontaneously use a tool, to get another tool, to get some food. This trick, known as "meta-tool use", is quite amazing as it suggests that the birds actually understand what's going on and have some form of analogical reasoning happening. This is a big deal - chimps, for example, often don't understand the physical properties of their tools (see for example, Daniel Povinelli's work on "Folk Physics"), but just appear to have learnt a sequence of actions.
To test this, Alex, Gavin, Jenny and Russell set up an experiment with two boxes containing tools; one short and one long. Only one of the tools could be used to get food out of a second box:
(image from Press Release [PDF])
Russell says:
Six out of seven birds tried to get the long stick with the short stick at their first attempt at solving the problem. To do this, they had to inhibit their normal response of trying to get the food directly with the short stick, and realize that they could use the short stick to get the long stick."
The website for this research group is here, and it has plenty of video clips, including this one, where Gypsy does the task the very FIRST time she sees it:
The abstract is available at Current Biology, "Spontaneous Metatool Use by New Caledonian Crows" (doi):
A crucial stage in hominin evolution was the development of metatool use—the ability to use one tool on another. Although the great apes can solve metatool tasks, monkeys have been less successful. Here we provide experimental evidence that New Caledonian crows can spontaneously solve a demanding metatool task in which a short tool is used to extract a longer tool that can then be used to obtain meat.
Six out of the seven crows initially attempted to extract the long tool with the short tool. Four successfully obtained meat on the first trial. The experiments revealed that the crows did not solve the metatool task by trial-and-error learning during the task or through a previously learned rule. The sophisticated physical cognition shown appears to have been based on analogical reasoning. The ability to reason analogically may explain the exceptional tool-manufacturing skills of New Caledonian crows.
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