This comes from a high school science project on a Franciscan monk science web-site, so it must be true... (Stop laughing!)
Apparently, some kid in Virginia took two groups of mice and subjected one to 10 hours of classical music per day, and the other to 10 hours of hard rock per day. Both groups of mice were routinely sent through a maze and it was found that after 3 weeks, the classical music mice had cut their maze navigation time down by 85%. The times for the hard rock mice meanwhile had gone up by a dazed and confused 100%!...
The experiment would have gone on longer but unfortunately... all the hard rock mice killed each other.