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])
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.”
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.