I don't understand what is so disturbing about the Crabbe test. They injected mouse with cocaine and they observed that the mouse was moving more than normal. They different in how much more. But why would they expect that the extra movement be constant and consistent?

Now if one set of mouse moved more, while an other started blowing orange soap bubbles from their ears that would be disturbing. But just that the average differed? Maybe I should read the paper in question.