Monkeys don’t care much for human music, but apparently they will groove to their own beat.

Previous experiments have shown that tamarin monkeys prefer silence to Mozart, and they don’t respond emotionally to human music the way people do. But when a psychologist and a musician collaborated to compose music based on the pitch, tone and tempo of tamarin calls, they discovered that the species-specific music significantly affected monkey behavior and emotional response.

“Different species may have different things that they react to and enjoy differently in music,” said psychologist Charles Snowdon of the University of Wisconsin-Madison, who published the paper Tuesday in Biology Letters with composer David Teie of the University of Maryland. “If we play human music, we shouldn’t expect the monkeys to enjoy that, just like when we play the music that David composed, we don’t enjoy it too much.”

Indeed, the monkey music sounds shrill and unpleasant to human ears. Each of the 30-second pieces below were produced with a cello and Teie’s voice, based on specific features from recordings of tamarin monkey calls. The first “song” is based on fear calls from an upset monkey, while the second one contains soothing sounds based on the vocalizations of a relaxed animal.

Fearful monkey music: Download mp3

Happy monkey music: Download mp3

“What David has done is to create compositions that are based on structural aspects of the calls but aren’t directly mimicking the calls,” Snowdon said. “These are compositions that are intended to test whether we can convey emotional meaning and induce emotional states in other species.”

The researchers played each piece, as well as several samples of human music, for 14 tamarin monkeys that hadn’t heard music before. An independent observer recorded monkey behavior for five minutes before and after playing each selection. The monkeys didn’t respond at all to Nine-Inch Nails, Tool or Samuel Barber’s “Adagio for Strings,” but oddly enough, they did become slightly calmer after listening to “Of Wolf and Man” by Metallica.

Monkey music, on the other hand, had a significant and predictable effect on behavior. After listening to the fear-based track, the animals became anxious and upset, as indicated by increased activity and nervous behaviors like urination and scent marking. After hearing the calm music, the monkeys became more relaxed and social.

“It’s not obvious that this would happen, but I don’t think it’s terribly surprising,” said neuroscientist Josh McDermott of New York University, who studies primates and music but was not involved in this study. Because the researchers designed the sounds to share acoustical properties with the noises monkeys make to express emotions, McDermott said it’s natural the animals would respond emotionally.

“I think that the most interesting thing that has come out of this study is some suggestions for animal care,” he said. “It’s very common for people to play music for animals that are in captivity, because they figure that they’ll be interested in it or enjoy it. But our work suggests that they aren’t that interested in human music or prefer not to listen to it at all.” However, if music was tailored specifically to the kinds of sounds that animals are used to hearing, McDermott thinks it might have a more positive effect.

Teie, a cellist in the National Symphony Orchestra, came up with the idea of composing music for monkeys because he wanted to test his theories about how certain basic elements of music can be used to manipulate emotions. But because most people have been listening to music for so long, and therefore have significant likes and dislikes that color their emotional responses, he decided to test his ideas on a totally different species.

Teie contacted Snowdon to access a library of monkey recordings, and he quickly realized that some components of monkey communication are similar to the musical features found in human voice patterns.

“I sent him sound files of monkey calls,” Snowdon said, “and without explanation or any context, he was able to listen to them and tell what the context was.”

Although the tamarin songs don’t sound much like music to us, Teie said he wasn’t just imitating the monkey’s calls. “The very nature of music itself is that it’s stylized, that it almost extracts the emotional parts of the sound and makes it impossible to identify.” Teie used the same patterns to create the monkey music as he uses when composing human music, and he wrote out each song for the cello so that other cellists could play it too.

Next, the researchers want to find out whether other animals respond to species-specific music. “One of the implications of this research is that we’ve been mindlessly playing human music and assuming that other species will react to it,” Snowdon said. “But we just don’t know.”

Teie has been in touch with the National Zoo about composing music for wild animals in captivity, and he’s already created a company that markets melodies made specifically for felines (musicforcats.com). Stay tuned for canine classical and rabbit rock.

Image: Bryce Richter/University of Wisconsin-Madison. Audio: Copyright David Teie/University of Maryland.



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