AWESOME!Crows may be smarter than apes
By Roger Highfield, Science Editor
Last Updated: 12:01am BST 17/09/2008
Researchers found evidence that the birds are able to outsmart people's closest relatives when it comes to finding a way to access food without it falling into a trap.
Many studies have investigated the remarkable ability of crows from the Pacific island territory of New Caledonia to make tools from leaves, and customise them with great dexterity to extract grubs and caterpillars.
Now a team from Auckland University, led by Prof Russell Gray, publishes what it says is "the most conclusive evidence to date" that the birds are indeed smart, showing that they can reason causally and use analogy in a way not seen even in our closest relatives, the great apes.
In the Proceedings of the Royal Society: Biological Sciences, Prof Gray, Alex Taylor and colleagues describe experiments that were designed to work out what was going through the birds' minds.
The scientists presented crows with the trap-tube problem, where an animal had to extract food from a horizontal tube in a direction that avoids a trap, which swallows up the treat so they cannot eat it.
This problem can be solved by associating the relation between particular features of the trap-tube, such as the position of the hole or colour of the rim of the hole, with food. Alternatively an animal may "understand" how the task works but, until now, here has been no conclusive proof that animals reason causally when solving complex problems such as the trap-tube.
In this study, six New Caledonian crows were presented with a trap-tube with three arbitrary features inside it.
When the crows were presented with variations of the problem where these features were removed, three of the crows continued to solve the problem, suggesting the crows had not simply learn to pull the treat away from these features.
The scientist then presented the crows with a trap-tube with two holes. One hole allowed food to fall through it and out of the trap, so the bird could eat it. The other hole had a base and so trapped food that was pulled into it.
The three smartest crows failed to consistently solve this problem and appeared reluctant to pull the food into either hole, suggesting they were using the holes to guide their actions.
Finally, the crows were presented with a trap-table problem. In this problem an animal has to choose between pulling food across a wooden table or pulling food into a hole set in the table.
In a recent study 20 individuals from the great ape species were unable to transfer their knowledge from the trap-table and trap-tube or vice versa, despite the fact that both these problems work in the same way.
Strikingly the crows in the University of Auckland study were able to solve the trap-table problem after their experience with the trap-tube. By solving the trap-table the crows demonstrated that they had not just learnt to pull away from the specific hole in the Perspex trap-tube, but could generalise what they understood to a novel problem.
"The crows appeared to solve these complex problems by identifying causal regularities" said Prof Russell Gray of the University of Auckland. "The crows' success with the trap-table suggests that the crows were transferring their causal understanding to this novel problem by analogical reasoning.
However, the crows didn't understand the difference between a hole with a bottom and one without. This suggests the level of cognition here is intermediate between human-like reasoning and associative learning."
"It was very surprising to see the crows solve the trap-table" said Alex Taylor, a PhD student at the University of Auckland. "The trap table was visually different from the trap-tube in its colour, shape and material.
Transfer between these two distinct problems, the trap-tube and trap-table is not predicted by theories of associative learning and is something not even the great apes have so far been able to do".
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