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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4 Responses to Meta-tool use in New Caledonian Crows

  1. Chris says:

    I wonder, is that really meta-tool use? Doesn’t meta-tool use usually mean modifying a tool with another tool? Does picking a tool up count as modifying it?

  2. alex says:

    Metatool use is defined as the use of one tool on another. In its most advanced form it does involve tool modification but there are simpler forms, such as gaining access to a useful tool.

    Simply picking up a tool would not modify it. New Caledonian crows do spend time modifying stick tools. They strip bark off stick tools and removing side branches. Modification involves changing the natural form of an object.

    Cognitively the difference between use and modification in metatool use is probably slim. The clever thing about both is that you have to get out of old habits. Normal tool use is directed towards food, just as most animal behaviour is directed to food (as long as you can’t have sex, in which case toss a coin). Redirecting tool use towards non-food objects that can potentially be useful has been seen in only humans, great apes and now, new Caledonian crows

  3. Chris says:

    I guess what I’m asking is whether you couldn’t explain the “meta-tool use” in the first experiment as something like chaining. It’d still be impressive, but cognitively, pretty different from meta-tool use. It would certainly mean that we wouldn’t have to have recourse to some sort of analogical reasoning to explain it. I don’t mean to imply that I think it has to be chaining, only that I’m not sure the experiments rule chaining and operant conditioning out as an explanation.

  4. alex says:

    I’m not sure exactly what you mean by ‘chaining’. We felt we did rule out operant conditioning – the control of a second toolbox showed that the crows were not probing in an exploratory fashion – they didn’t probe because the toolboxes in themselves were interesting, they probed based on the contents of the toolbox. Thus learning based on trial and error seems very unlikely. I would be interested to hear how you think chaining and operant conditioning explain the performance of the crows.

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