This is ridiculous. Obviously if you want to test whether a raccoon understands the concept of displacing water with rocks you can't just have one experimental setup. You have to present the raccoon with very different cases where it could apply this concept and see if it has generalized or whether it has to learn each case on its own. (And you may find that there is no bright line; in some relatively similar experimental setups the raccoon may immediately start piling rocks into something and in more different ones requiring more ingenuity it might not. And the same thing goes for human understanding: there is no sharp line between grasping a concept at all and being able to cleverly use it.)
Tell me about it. I often thought I understood the concept from the lectures, and then when faced with the problems on an exam realized I was unable to apply it.
I learned the hard way to do all the homework problems.
