Mick Hartley

Are crows smarter than apes? Possibly:

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.

In a further study, a number of readers were presented with this article. They were then questioned as to the nature of the experiments, and were unable to provide any satisfactory account. Indeed they described themselves as "perplexed" and "confused", and were in general at a loss to make any sense of what they'd just read, due to what they described as the article's "total incomprehensibility".

Some passing crows, however, picked it up and dropped it through a trap-door, thus demonstrating their superior intelligence.