A study of people in 15 countries showed that while everyone prefers the rhythm of simple integer ratios, people in different societies may have different biases about rhythm.
When listening, the human brain seems inclined to hear and produce rhythms made up of simple integer ratios—for example, a series of four beats separated at equal intervals (forming a 1:1:1 ratio).
However, according to a large-scale study conducted in 15 countries by researchers from the Massachusetts Institute of Technology (MIT) and the Max Planck Institute for Empirical Aesthetics, the proportion of people who like it in different societies can vary greatly. The study included 39 groups of participants, many of whom came from societies where tradition **contained unique rhythmic patterns not found in the West**.
Our study provides the clearest evidence for some degree of universality in perception and cognition, in the sense that each group of participants tested exhibited a bias against integer ratios. "It also provides a glimpse into the differences that can occur between different cultures, which can be quite substantial," says Nori Jacoby, lead author of the study, former MIT postdoc and now head of the research group at the Max Planck Institute for Empirical Aesthetics in Frankfurt, Germany.
The brain's preference for simple integer proportions may have evolved into a natural error-correcting system that makes it easier to maintain consistency, which is often used by human societies to transmit information.
When people make **, they often make small mistakes. Josh McDermott, associate professor of brain and cognitive science at MIT and a member of the McGovern Brain Institute and Center for Brains, Minds, and Machines at MIT, said: "Our findings are consistent with our view that mental representations have some degree of robustness to these errors, but this robustness somehow drives our pre-existing ideas about the structures that should be found in **." ”
McDermott is the senior author of the study, which was published today in the journal Nature Human Behavior. The research team also includes scientists from more than two dozen institutions around the world.
A global approach
The new study stems from a smaller analysis published by Jacoby and McDermott in 2017. In that article, the researchers compared the rhythmic perception of a group of listeners from the United States and Tsimane, an indigenous society located in the Amazon rainforest in Bolivia.
To measure how people perceive rhythm, the researchers devised a task in which they randomly set a series of four beats and then asked the listener to call back what they had heard. Then the rhythm produced by the listener is ** to the listener, and they beat it again. After several iterations, the eavesdropped sequence is dominated by the listener's intrinsic biases, also known as a priori.
"The initial stimulus pattern was random, but in each iteration this pattern was driven by listener bias, so it tends to converge to a particular point in the possible rhythmic space," McDermott said. "This gives you an idea of what we call a priori, the intrinsic implicit expectation of rhythm in people's minds. ”
When the researchers first did this experiment, they tested American college students, and they found that people tend to use simple integer ratios to produce time intervals. In addition, most of the rhythms they produce, such as the ratio of 1:1:2 and 2:3:3, are common in the West**.
The researchers then went to Bolivia and asked members of the Tisman society to perform the same task. They found that the Tessmans also produced rhythms with simple integer proportions, but they preferred different proportions that seemed to be consistent with those recorded in the few extant Tisman records.
At this point, it provides some evidence that there may be a very general tendency to favor these small integer ratios, and that there may be some degree of cross-cultural variation. "But because we're just looking at another culture, it's really not clear how to look at it on a larger scale," Jacoby said.
To get a bigger picture, MIT research teams began looking for collaborators around the world to help them collect more data on diverse populations. They ended up studying listeners from 39 groups in 15 countries across five continents: North America, South America, Europe, Africa, and Asia.
"This is really the first study of its kind, because we did the same experiments in all these different places, people on the ground in those places," McDermott said. "There had never been an experiment on a similar scale before, which gave us a chance to see the extent of the difference that might exist.
Comparison of cultures
As they did in their original study in 2017, the researchers found that in each group they tested, people tended to gravitate toward a simple integer proportional rhythm. However, not every group exhibits the same bias. People from North America and Western Europe may have heard the same type of **, and they are more likely to produce the same proportions of rhythm. However, many groups, such as those from Turkey, Mali, Bulgaria, and Botswana, show a preference for other rhythms.
Jacobi said, "In some cultures, there are special rhythms that end up in the mental representation of rhythm. ”
The researchers believe their findings reveal a mechanism that the brain uses to help with perception and production.
"When you hear someone playing a mistake, you mentally correct those mistakes and map them to where you subconsciously think they should be," McDermott said. "If you don't have something like this and you're just faithfully representing what you're hearing, these errors can spread, making it harder to maintain a ** system. ”
In the groups they studied, the researchers noted not only college students because they were easily studied in large numbers, but also people living in traditional societies, who were more difficult to reach. Participants from traditional groups showed significant differences with university students living in the same countries, as well as those living in those countries but taking the test online.
"This article makes it very clear that if you only look at the results of undergraduates around the world, you are vastly underestimating the diversity you see," Jacobi said. "We tested the ** population in Brazil and India, and the results were the same, because you were dealing with a population with access to the internet, and they were probably more exposed to the West**.
Researchers now want to take this global approach and do more research on different aspects of perception.
If you just test college students or netizens around the world, the situation will look even more similar. "I think it's really important for the field to recognize that you actually need to go out into the community and experiment there, rather than doing low-hanging fruit research in college or on the internet," McDermott said. ”
The study was supported by the James S. MacDonald** Society, the National Science and Engineering Research Council of Canada, the National Research Society of South Africa**, the National Science ** of the United States**, the National Research and Development Agency of Chile, the Austrian Academy of Sciences, the Japan Association for the Promotion of Science, the Keio Global Institute, the Arts and Humanities Research Council of the United Kingdom, the Swedish Research Council, the National Science and Engineering Research Council of Canada, the National Science and Engineering Research Council of Canada, the National Academy of Science of the United States, Funded by the National Agency for Research and Development of Chile, the National Agency for Research and Development of Chile, the National Agency for Science and Development of Chile, the National Agency for Science and Development of Chile, the National Agency for Science and Development of Chile, the National Agency for Science and Development of Chile. and John Fair**.