[Update: A slightly more technical piece on this topic has been published in PNAS]
BBC News report that, in recent experiments, rooks (a species of crow) have demonstrated surprisingly sophisticated tool use. For instance, the rooks learned to insert a stone into a plastic tube to gain access to a second stone, which they then inserted into another tube to finally retrieve a juicy maggot.
I am a big fan of corvids. But what do these new findings say about their intelligence? What do rooks understand about causes and effects in the physical world? The controversy that this experiment touches upon boils down to the question: How much did the rooks figure out on their own, and how much did the researchers help them? Time-honored animal training techniques, in fact, allow to "shape" (as animal psychologists say) behavior of amazing complexity. Just think of what animals do in movies. The key technique is to break down a complex behavior into small, simple components that the animal can learn without much difficulty (and without much understanding).
The rooks' tool use behavior was shaped at least to some extent. For instance, stones where initially placed near the rim of the plastic tube, so that they could easily (and accidentally) be nudged down the tube. After the rooks mastered this step, stones were placed besides the apparatus, and finally they were moved further so that rooks learned to pick them up and transport them for some distance to the tube.
Such a use of shaping does not exclude that, by the end of the experiment, the rooks had developed an understanding of the task. For instance, they reliably chose stones small enough to fit into the tube. Thus I am not criticizing this brilliant experiment. I am
an even bigger fan of corvids now. But we do not know whether the rooks could have understood everything on their own.
Indeed, we do not know what "understanding" means. Animal psychologists have traditionally contrasted "insight" and "trial and error" learning. Insight is what happens when you realize the solution to a problem in your head, using your knowledge of causes and effects in the world. It is considered an advanced cognitive skill, available to humans and perhaps apes and, now, corvids. Trial and error is a more mundane process, whereby an organism learns to repeat behavior which, performed randomly or accidentally at first, has brought about desirable consequences. Shaping exploits animals' abilities of trial and error learning, by rewarding them only for the behavior we want them to produce (a classical example here). Can we understand animal intelligence by contrasting insight and trial-and-error learning? We do not know. Perhaps they are not fundamentally distinct phenomena, and a deeper understanding will come from looking at the problem from a different angle.
Main reference: Insightful problem solving and creative tool modification by captive nontool-using rooks, by C. D. Bird & N. J. Emery.