Listen to the two sound clips above. Chances are, you enjoyed the first one a lot more—and so it is for most people you know. That has led researchers to believe that humans have an innate preference for so-called consonant sounds. But a new study of a remote Amazonian tribe reveals that this preference may not be so innate after all; people who have had no exposure to the outside world think both noises above are equally pleasant. The findings suggest that culture, not biology, determines at least some of our musical taste.
“I think their conclusions are very reasonable,” says psychoacoustician Brian Moore at the University of Cambridge in the United Kingdom. “The paper is unusual in that they’ve gone to great lengths to find a group of people who haven’t had exposure to Western music and whose own music doesn’t have much in the way of harmony in it.”
What makes the result even stranger is that there are some clear mathematical patterns behind sounds we traditionally think of as consonant. Sounds are made of vibrations in the air, and the peaks and valleys within those vibrations occur at different intervals depending on the sound’s frequency. The vibrations of a high-pitched sound come rapidly, or with high frequency, whereas a low-pitched sound vibrates at low frequency.
If you look at the ratio of frequencies between two tones, some interesting patterns emerge. Tone pairs that form simple, whole number ratios (2:1, 3:2, 4:3) tend to mix to create sounds that Western music has agreed are consonant and pleasing to the ear. The consonant example above is made of tones with 3:2 frequency ratio. Triads—like your classic G chord—are made of a root tone (G), its third (B), and its fifth (D). Dissonance tends to occur when these ratios get messier. The dissonant example above has a frequency ratio of 16:15. You can use these definitions to define consonance and dissonance objectively, but most Westerners know instantly whether a sound is consonant or dissonant—and they prefer consonance. But the new study suggests that our preference for one over the other is shaped by our experience with music.
To conduct the work, auditory neuroscientist Josh McDermott at Massachusetts Institute of Technology in Cambridge and colleagues turned to the Tsimane (pronounced CHEE-MAH-NAY) people, who live in the Amazonian rainforest in northwest Bolivia along the Maniqui River. Their villages are extremely remote, with some accessible only by canoe. They’re one of the last isolated groups left on the planet, and their experience with Western music is, suffice it to say, highly limited. Their own music doesn’t contain harmony, and instead is performed exclusively by soloists—the band scene in Tsimane villages is literally nonexistent.
The researchers asked 64 Tsimane participants to rate the pleasantness of consonant and dissonant sounds played over headphones. The team then compared these results with ratings from groups of people with heavy exposure to Western music including U.S. musicians, U.S. nonmusicians, and residents of Bolivia’s capital city, La Paz.
Remarkably, the Tsimane seem to have no preference for consonance over dissonance, the scientists report today in Nature. “They don’t seem to care whether that ratio is a simple one or one that would be judged as dissonant by Western listeners,” Moore says. As expected, Westerners heavily favored the consonant pairing.
To demonstrate that the Tsimane understood the task and did have opinions about sound, the researchers also had both groups rate the attractiveness of gasps versus laughter and rough acoustic tones versus smooth. Roughness is a harsh quality that emerges in music when two tones have very close, but not identical frequencies. The resulting sound waves overlap in a way that causes the volume to rapidly rise and fall, giving the sound an unpleasant quality. In these trials, the Tsimane’s aesthetic tastes mirrored the Westerners’, consistently preferring laughter and smooth tones. That suggests that the Tsimane people do have preferences for some sounds over others and clearly understood the directions from the researchers.
The researchers also took care to show that the Tsimane could actually make out the difference between consonant and dissonant tones—demonstrating that they weren’t just tone deaf. They weren’t as good at the task as Westerners, but scored far better than random chance. “Their hearing seems to be like that of Western listeners,” Moore says.
The results, the researchers suggest, indicate that Western preference for consonance may be caused by our exposure to music that focuses on it. We like what we know, and we know consonance. These preferences may then be reinforced by media: McDermott points out that the harmonious pieces of music in film or advertising usually occur during happy, interesting, and funny moments, for instance. “I think we now have pretty good evidence that there’s this strong cultural component,” he says.
This raises the question of how consonance became popular in Western music to begin with, which will likely be the subject of further study. But Moore points out that many musical instruments began as just one tube (think of a bugle) or one string, and thus only allowed musicians to play notes derived from the fundamental frequency generated by the tube or string vibrating openly, with new notes naturally occurring at the harmonic lengths. “The inherent notes that you get out of simple instruments often have simple frequency ratios to each other because of the physics of the instrument,” Moore says. “And so it may be that that initially drove the sounds that were made by instruments.”
For now, although the Tsimane remain isolated from Western music, it seems they may be the truest believers in the famous Miles Davis quote on music: “Do not fear mistakes. There are none.”