After decades of studying primate behavior at the University of Wisconsin–Madison, Charles Snowdon closed his colony of cotton-top tamarins (Saguinus oedipus) in 2008. The little monkeys, looking like better-groomed versions of Spike from the movie Gremlins, had given Snowdon a glimpse into various aspects of their social lives, from parenting and social learning to hormones and vocal communication. But one of his last studies on the species took him in a totally different direction.
Several years earlier, Snowdon had received a call completely out of the blue from a cellist with a scientific bent named David Teie, who had been studying the various components of music and how each relates to the human experience and affects our emotions. Take pulse, for example—the maternal heartbeat to which every fetus develops. “Even though it’s not part of our language, you can find it in all [forms of] music,” says Teie.
He explains that there are about two dozen of these musical components, acting like ingredients for song recipes, and Teie felt he had reasonable explanations for why each of them is part of human music. “If I had indeed figured out the recipe [for humans], I should be able to replace the ingredients with ingredients designed for another species,” Teie reasoned. And so he called up Snowdon to ask for help.
The cellist asked the biologist if he would be willing to test the effects of music on the monkeys. Snowdon liked the idea. The tamarins in his colony had never been exposed to human music. “They were completely naive and, therefore, they would be good test subjects to test emotionality,” Snowdon says. Teie composed several songs, two mellow and two upbeat, using what he imagined to be tamarin musical ingredients, such as tempos matching their calls and tones that exist in their vocal range.
When Snowdon played snippets of the songs for the animals, he found the monkeys displayed an increase in anxious behaviors after the energetic songs. And compared with baseline behavior, they appeared more relaxed after the calming music (Biol Lett, 6:30-32, 2010). “It suggests animals other than humans can appreciate music, at least the emotional aspects,” says Snowdon. “It’s a way of arguing that the emotional aspects of music have a long evolutionary history.”
Their next project was to test this idea on cats. Teie made music this time with components resembling purrs, suckling sounds, and female vocalizations. “It took five people and four software programs about two weeks to get the two-second sample of the purr I was really happy with, that had a pitch in it and all the contours I wanted,” says Teie. His hard work paid off; when cats were presented with various songs, they gravitated toward a speaker playing music Teie wrote for the cats more than toward a speaker playing Bach’s Air on a G String or Gabriel Fauré’s Élégie (Appl Anim Beh Sci, 166:106-11, 2015).
“Since animals do not typically perceive sounds in the same way as people, it makes a lot of sense to design music that is more tailor-made for the species under target,” Deborah Wells, who studies animal behavior at Queen’s University Belfast, wrote in an email to The Scientist. In her own work, she’s found that dogs in kennels and elephants and gorillas kept in zoos seem to benefit from classical music. But she also says that other studies have found no effect, or that certain types of music can agitate animals. “It is still unclear how music exerts its effects on animals, and more research is needed to explore the potential mechanism/s by which acoustic stimuli influence animal well-being.”
Emma Wallace, a graduate student at the University of York, says there’s been evidence that music has a positive effect on chimpanzees’ welfare. One possibility is that music might mask unpleasant sounds, say, of a ventilation system or a noisy animal shelter. In a recent study, she wanted to see how zoo-housed chimpanzees would react. She had pop and classical music played in the chimps’ enclosures, but the animals didn’t show much of a response one way or another. “Generally, it looks like music is not something that they’re enjoying,” she says, “but it’s not having a negative effect on their welfare either.”
Roian Egnor, who studies mouse vocalization at Janelia Research Campus, is skeptical about nonhuman animals’ enjoyment of music. “Any sound at all is going to interfere with your ability to hear a predator coming,” she says. “My bet? I would need extraordinary evidence to show that an animal actually likes music. I’d love to see it.”
Teie, for one, was convinced by Snowdon’s behavioral data that the feline test subjects were indeed drawn to his music. So his next step, obviously, was to make them an album. Music for Cats dropped in October of last year, earning a spot on the U.K.’s Top 40. It was the first time music intended for animals made the chart, he claims, “so in that sense it’s the most popular animal music ever,” he says jokingly. “But Adele is not worried about the competition.”