David Merrell conducted an experiment in which he timed seventy-two mice running through a maze. He divided the mice into three groups and let each mouse run through the maze (establishing an average time of ten minutes). He then left one group alone, played classical music to one group, and played hard rock music to the other group.
When he timed them again, the mice that had had not listened to any music took about five minutes less to run through the maze than they had before. The mice that listened to classical music improved their time by eight and a-half minutes, while the mice that listened to hard rock music took three times as long to complete it as they had before.
The mice that listened to hard rock music did not sniff the air to find trails from mice that had gone before them as the other mice did. David said, “It was like the music dulled their senses. 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.”
During this experiment each mouse was housed in separate aquariums. That is because when David had previously attempted to perform a similar experiment he kept the mice in each group together, and those mice that listened to the rock music killed each other.