Cross-cultural research reveals commonalities and diversity in musical mental representations

When listening to music, the human brain seems to be biased towards hearing and generating rhythms made up of simple integer ratios. For example, a series of four beats separated by equal time intervals (forming a 1:1:1 ratio).

But a large-scale study conducted in 15 countries led by researchers at the Massachusetts Institute of Technology (MIT) and the Max Planck Institute for Empirical Aesthetics suggests that the preferred ratio can vary widely from society to society. The study included 39 groups of participants, many of whom came from societies whose traditional music includes unique rhythmic patterns not found in Western music.

“Our study provides the clearest evidence to date of some degree of universality in music perception and cognition, in that all groups of participants tested show an integer ratio bias. “It also provides a glimpse into the variation that can occur between cultures,” said the study’s lead author, a former MIT postdoctoral fellow and now a professor in Germany. says Nori Jacoby, research group leader at the Max Planck Institute for Empirical Aesthetics in Frankfurt.

The brain’s bias toward simple whole-number ratios may have evolved as a natural error-correction system that helps maintain consistency in the music that human societies often use to convey information.

When creating music, people often make small mistakes. Our results are consistent with the idea that our mental representations are somewhat robust to mistakes in them, but they do It is robust in the sense that it drives ”

Josh McDermott, Associate Professor of Brain and Cognitive Sciences, Massachusetts Institute of Technology, and member of the McGovern Institute for Brain Research and the Center for Brains, Minds, and Machines, Massachusetts Institute of Technology

Mr. McDermott is the lead author of this study and today natural human behavior. The research team also included scientists from more than 20 institutions around the world.

global approach

This new study expands on a smaller analysis published in 2017 by Jacoby and McDermott. In that paper, researchers compared the rhythm perception of a group of listeners from the United States and the Tsimane people, an indigenous community located in the Amazon rainforest of Bolivia.

To measure how people perceive rhythm, researchers played a series of four randomly generated beats and asked listeners to tap back on the sounds they heard. I devised it. The rhythm generated by the listener is played to the listener, who then taps it again. Over several iterations, the tapped sequence became dominated by the listener’s internal bias, also known as the prior distribution.

“The initial stimulus pattern is random, but with each repetition the pattern is pushed by the listener’s biases and tends to converge at a certain point in the space of possible rhythms,” McDermott says. “That will give you a complete picture of what we call the prior distribution, which is a collection of internal, implicit expectations about the rhythm that people have in their heads.”

When researchers first conducted this experiment with American college students, they found that people tended to generate time intervals that were related by simple integer ratios. Additionally, most of the rhythms they produce are common in Western music, such as the 1:1:2 and 2:3:3 ratios.

The researchers then traveled to Bolivia and asked members of the Tsimane community to perform the same task. Although the Tsimane also produced rhythms with simple integer ratios, the ratios they preferred appear to be different and consistent with those recorded in the few extant records of Tsimane music. I discovered something.

“At that point, we had evidence that the preference for these small integer ratios may be very widespread and that there may be some variation across cultures. But we “We were just looking at this other culture, so it wasn’t really clear what this was going to be on a broader scale,” Jacoby says.

To get the full picture, the MIT team began searching around the world for collaborators to help collect data on more diverse populations. They ultimately surveyed 39 groups of listeners representing 15 countries on five continents. North America, South America, Europe, Africa, Asia.

“This is the first study of its kind in that we performed the same experiment on people on the ground in different locations,” McDermott said. “It’s never been done before on this scale. This gives us the opportunity to see the degree of variation that can exist around the world.”

cultural comparison

Similar to the original study in 2017, the researchers found that across all groups tested, people tended to bias towards simple whole number ratios of rhythms. However, not all groups showed the same bias. People in North America and Western Europe, who were more likely to have been exposed to the same types of music, were more likely to produce rhythms at the same rate. However, many groups, such as Turkey, Mali, Bulgaria, and Botswana, showed a bias toward other rhythms.

“There are certain cultures that have certain rhythms that stand out in their music, and those end up showing up in the mental expression of rhythm,” Jacoby says.

Researchers believe their discovery reveals a mechanism the brain uses to help perceive and generate music.

“When you hear someone playing something and there’s an error in their playing, you correct it in your head by mapping it to where you implicitly think it should be. “That’s what happens,” McDermott said. “If we didn’t have something like this and were just faithfully representing what we heard, these mistakes could propagate and make it even more difficult to maintain the music system.”

The researchers were careful to include in their study population not only university students, who tend to study in large groups, but also people living in traditional societies, where contact is difficult. Participants in these more traditional groups showed significant differences from college students living in the same countries and from people living in those countries who took the test online.

“What’s very clear from this paper is that if you look only at results for undergraduates around the world, you’re vastly underestimating the diversity that would otherwise be seen,” Jacoby said. “And the same was true in experiments where we tested groups of people online in Brazil and India, because we were working with people who had access to the internet and were probably more exposed to Western music.”

The researchers now hope to take this global approach to conduct additional research into different aspects of music cognition.

“If you’re just testing college students and people online around the world, the picture looks more homogeneous. In this field, we recognize that we need to actually go out into the community and do experiments there.” “I think it’s really important to do that. We’ve had the low-hanging fruit of doing research with people in universities and on the internet,” McDermott said.

This research was supported by the James S. McDonnell Foundation, the National Science and Engineering Research Council of Canada, the South African National Research Foundation, the U.S. National Science Foundation, the Chilean National Agency for Research and Development, the Austrian Academy of Sciences, the Japan Society for the Promotion of Science, the Keio University Global Research Institute, Arts and Humanities Research Council UK, Swedish Research Council and John Fell Foundation.