I think that Euph has a point and that the experiment did take place, yet the story was fitted to the objective of the speaker.
I do have some problems with the interpretation of the results however.
It shows point-blank that hard rock has a negative effect all around. I can't think of a positive
effect that hard rock has" on learning.
This is unsupported. It doesn't show that 'hardrock has a negative effect all around', rather, it shows at most that exposure to hardrock has a negative effect on the pathfinding abilities of mice. There was no learning involved as they were already familiar with the maze. A possible effect on memory, could be argued for.
One should also be aware that hardrock and other music is a complex pattern of tones, rythems and notes. The observed effect could be due to one element, a combination of two or more of those elements or the entire complex. For example Hardrock tends to have a faster and harder beat as opposed to most classical music. Maybe this caused a sense of danger in the mice (previous studies has shown that rythem and beat has an effect on bloodpressure, hart beat rythem and adrenalin levels) thereby inducing disorientation and cannibalistic behaviour (not uncommon in rats and mice).
Extrapolating this experiment from mice to humans is not warrented either as already pointed out. We are familiar with music as a species, we even make our own. Mice do not.
Greven