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Culture, not biology, may define which musical chords sound sweet — and which don't

Culture, not biology, may define which musical chords sound sweet — and which don't
This image shows the experimental setup, in which sounds were presented to the study participants using headphones. (Josh McDermott)

When it comes to musical aesthetics, beauty is in the ear of the beholder. A new study finds that people who haven't been exposed to Western music don't find certain "discordant" sounds unpleasant at all.

The findings, described in the journal Nature, show that Western musical sensibilities aren't hardwired into the human auditory system. They may actually be a cultural phenomenon.

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Humans have been making music for tens of thousands of years. It's a quality, along with language, that seems to define our species. And while music can be found nearly any place on earth, where you find human societies, its origins and true nature remain a mystery.

"Music is present in every culture, but the degree to which it is shaped by biology remains debated," the study authors wrote.

The ideas of consonance and dissonance play a key role in that debate. If you've ever been listening to someone play the piano and he hits a wrong note in a chord, you'll probably notice immediately — and register it as unpleasant, or dissonant. On the other hand, consonant musical combinations are thought to be pleasant-sounding and can even be described in mathematical terms that also are beautiful in their elegance and simplicity, according to Robert Zatorre of the Montreal Neurological Institute at McGill University, who was not involved in the study. The perfect fifth, for example, involves two notes whose frequencies are in a ratio of 3:2. The major third involves two tones in a 5:4 ratio. Both are thought to be more consonant than two notes in a 16:15 ratio, known as the minor second.

Hear the difference:

"Aesthetic responses to consonance are commonly assumed by scientists to have biological roots, and thus to be universally present in humans," the study authors explained. "Ethnomusicologists and composers, in contrast, have argued that consonance is a creation of Western musical culture. The issue has remained unresolved, partly because little is known about the extent of cross-cultural variation in consonance preferences."

Part of the reason it's so hard to make those cross-cultural comparisons is because Western cultural influences, music included, have spread across the globe. Even in places such as India and China, with very distinctive musical heritages and traditions, people still know who Beethoven and Britney Spears are.

So for a paper led by Josh McDermott of MIT, a team of researchers decided to set up an experiment that included people with somewhat limited or virtually no access to Western music. Their study participants included people from the United States, separated into two groups: those with musical training and those with little to none. They compared the U.S. listeners to three other groups: city-dwellers in La Paz, the capital city of Bolivia, which has plenty of exposure to Western culture; residents in San Borja, a town in the countryside that is accessible only by airplane during much of the rainy season; and members of the Tsimane', a native population in Santa Maria, a remote village in the Amazon rainforest that can be reached only by canoe.

Of these groups, the Tsimane' were a particularly interesting comparison to the U.S. residents — not just because they were so remote as to be largely uninfluenced, but because their musical culture lacks harmony, polyphony and group performances. In fact, the researchers tried to get the Tsimane' musicians to play or sing together but failed to persuade them.

"They were usually reluctant to do so (despite being eager to perform solo songs for each other), and on the few occasions when we could elicit concurrent performances, they were unable to coordinate," the authors wrote. "Our experience suggests that group musical performance in Tsimane' culture is rare at best."

If the Tsimane' never played or sang with or over one another, then perhaps they wouldn't even have a concept of what it means to harmonize — and to do so in a way that's aesthetically pleasant. This made them extremely valuable participants in this musical test.

The researchers played two- or three-note chords (some played by a synthesizer, others sung by humans) that would be, according to Western standards, either "consonant" or "dissonant," and asked listeners in each group to put on headphones and rate the pleasantness of the sound on a four-point scale.

The U.S.-based participants had the strongest preference for the consonant chords, with the musicians showing the most extreme bias. And there seemed to be a clear gradient in the listeners' responses: The city dwellers and townfolk had a statistically significant but far less pronounced preference for consonant sounds. The Tsimane', however, didn't seem to distinguish between the supposedly pleasant and unpleasant chords at all.

To make sure all the participants understood the task, scientists also had listeners rate non-musical human sounds like laughing and gasping; the laughs were consistently rated as more pleasant by all the groups, proving that all the participants were indeed on the same page. The Tsimane', then, really didn't hear an aesthetic difference between the concordant and discordant tones.

"The results indicate that consonance preferences can be absent in cultures sufficiently isolated from Western music, and are thus unlikely to reflect innate biases or exposure to harmonic natural sounds," the authors concluded. "The observed variation in preferences is presumably determined by exposure to musical harmony, suggesting that culture has a dominant role in shaping aesthetic responses to music."

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There might be an interesting analogy for this phenomenon in language development, Zatorre explained. After all, babies have the capacity to hear a vast variety of distinctive sounds, but tend to lose them as they acquire their first language. That's why Japanese speakers learning English might sometimes have trouble navigating the "r" and "l" sounds at first because that particular distinction is irrelevant in Japanese. Similarly, if Tsimane' infants never heard harmonies in their youth, then perhaps there would be no reason for the brain to hold on to the ability to draw distinctions between the aesthetics of different combinations of notes.

"But does this idea rule out the possibility of innate factors?" Zatorre wrote in a commentary on the paper. "Not necessarily, because, despite their lack of preference for harmonically related tones, the Tsimane' did display a similar dislike to Western listeners for roughness — the sensation of sound that is elicited by tones that are close together in frequency, especially minor and major seconds. This finding suggests that there are probably some innate biological constraints on which environmental input operates."

It would be interesting to explore whether consonance and dissonance (as we think of them) arise in those cultures that do start to use harmonies in music, he added.

"Although many questions remain, this work represents an important contribution to our understanding of how the diversity of human cultural expression can influence perception," he wrote.

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