Monkeys prefer heavy metal to classical music, according to researchers at the University of Wisconsin whose findings are published this week in Biology Letters. Scientists played a selection of music to a group of South American cotton-top monkeys but the only sound that got a reaction were from the heavy metal band Metallica. They were seemingly disinterested in Led Zeppelin, Miles Davis and Bach, but after the beautiful sound of Master of Puppets by Metallica was played the monkeys calmed down. "Monkeys interpret rising and falling sounds differently than humans. Oddly, their only response to several samples of human music was a calming response to the heavy-metal band Metallica," said Professor Charles Snowdon, from the University of Wisconsin-Madison. Rather than making them excited or aggressive, the heavy metal tracks had a comforting effect. Dr Snowdon, who teamed up with National Symphony Orchestra musican David Teie, also played the monkeys music composed specifically for them. Although they enjoyed Metallica, they were much more interested in these pieces. A melody  based on the short calls of scared monkeys led to anxiety levels rapidly growing, researchers found, while one based on long calls the creatures make when they are happy had a calming effect. Frans B.M. de Waal, a professor of psychology at Emory University who studies animals, said the findings appear to say more about how monkeys respond to the sounds they make than they do about music or the evolution of music. Dr Snowdon no longer has a monkey colony to use in his research, but he said his co-author David Teie is exploring the concept of music for cats. "If we understand how we can affect their emotional states through using musical sound and aspects of our speech, maybe those of us living with companion animals can have a better relationship with them, too," Snowdon said. The aim of the research, according to Professor Snowdon, is to   _  .
build better ties between animals and humans compare monkeys and cats in term of music develop new music based on animals' calls find better ways to keep animals under control