Science/AAAS

Rhythm might be hardwired in humans

Have you ever wondered why a strange piece of music can feel familiar—how it is, for example, that you can predict the next beat even though you’ve never heard the song before? Music everywhere seems to share some “universals,” from the scales it uses to the rhythms it employs. Now, scientists have shown for the first time that people without any musical training also create songs using predictable musical beats, suggesting that humans are hardwired to respond to—and produce—certain features of music.

“This is an excellent and elegant paper,” says Patrick Savage, an ethnomusicologist at the Tokyo University of the Arts who was not involved in the study. “[It] shows that even musical evolution obeys some general rules [similar] to the kind that govern biological evolution.”

Last year, Savage and colleagues traced that evolution by addressing a fundamental question: What aspects of music are consistent across cultures? They analyzed hundreds of musical recordings from around the world and identified 18 features that were widely shared across nine regions, including six related to rhythm. These “rhythmic universals” included a steady beat, two- or three-beat rhythms (like those in marches and waltzes), a preference for two-beat rhythms, regular weak and strong beats, a limited number of beat patterns per song, and the use of those patterns to create motifs, or riffs.

“That was a really remarkable job they did,” says Andrea Ravignani, a cognitive scientist at the Vrije Universiteit Brussel in Belgium. “[It convinced me that] the time was ripe to investigate this issue of music evolution and music universals in a more empirical way.”

In the new study, Ravignani and his colleagues focused on the six consistent features identified by Savage’s team. They gathered up 48 nonmusicians from the University of Edinburgh and asked them to play a mildly embarrassing game of telephone. Groups of eight students had to repeat a series of 12 random beats generated by a computer that adhered to none of the the six universals. The first person in each group tried to imitate the computer's “music,” the next person tried to imitate the drumming of the first, and so on. By the time the final person laid down their riffs, something remarkable happened: The random beats had transformed into easy-to-learn, highly structured patterns. What’s more, those patterns reflected all six universals, Ravignani and his team write online today in Nature Human Behavior.

“That was pretty amazing,” Ravignani says. “In a nutshell, we could find that what you get in the lab … exhibits exactly the same features of the world music.”

But do those similarities arise from biology, or from culture? Even if you aren’t a musician, your exposure to music as an adult is “massive,” writes William Tecumseh Sherman Fitch III, an evolutionary biologist and cognitive scientist at the University of Vienna, in an accompanying perspective. But he adds that although our musical preferences might not be “hard-coded” into the human genome, biology may still set the stage for later cultural selection: “Humans may have a … propensity to structure acoustic input in certain ways, leading over time to a cultural emergence of universals.”

Ravignani agrees, citing working memory as one example of a biological constraint that could shape our musical preferences. If working memory can process just five to seven elements at a time, as many scientists say, it would be impossible for our minds to keep track of 12 beats in any given moment. But if we transform those beats into regular groupings of smaller, repeating elements, then we should be able to compress the information to fit the limited capacity of our working memory. “This is the best working hypothesis we have,” says Ravignani, who adds that the biological hypothesis “dovetails nicely” with other research in cognitive science and psychology.

To reduce the influence of musical exposure, Ravignani is preparing to redo the experiment with subjects from different regions of India, China, Russia, Europe, and Africa. Ideally, those subjects would include people from isolated indigenous cultures that are not exposed to Western pop music, Savage says. After that, Ravignani’s next project is even more ambitious: to repeat the process with nonhuman animals. Figuring out how chimpanzees or harbor seals—some of the few species that can synchronize to a beat—transmit music might help us reconstruct the early steps in our evolution of musical cognition, he says, perhaps bringing us closer to understanding both how and why we create music as we do.