MANY SCIENTIFICALLY INTERESTED PEOPLE HAVE SEEN them: films of different species of corvids that put objects in test tubes in order to raise the water surface to get at a floating piece of food. It looks as if the birds assemble an overview of the situation, contemplate how to best solve the problem, and then implement their solution. The experiments have been argued to constitute evidence that these birds can solve problems on about the same level as primates; they have even been compared to 5-7 year old children. But now new analyses from Stockholm University indicate that these assertions must be reconsidered.
The experiments are termed "Aesop's fable" experiments, from the ancient Greek storyteller Aesop's fable of a thirsty crow that finds a pitcher of water. By putting pebbles in the pitcher, the crow manages to raise the water level enough to drink. The moral of the story is that inventiveness and persistence will be rewarded.
Inventive and persistent also describes the scientists who thought of using a similar setup to test corvid cognitive abilities. The experiments have been carried out on rooks, Eurasian jays, and New Caledonian crows. The problem is that if you put a corvid in front of this type of problem in an experimental arena with a test tube filled with water, the birds will normally not think of dropping in pebbles--even if there is a tasty morsel floating on top, just out of reach.
In fact, if the birds weren't given any clues, they would probably die of thirst or starvation before figuring out a solution. The behavior of raising the water level using pebbles is simply not part of the natural behavior of corvids. To test if birds can solve this kind of problem the experimenters must...