800 million songs to hear the rhythm of the planet

We humans like to hear more animated music during the day. Fridays are the liveliest and, as summer approaches, we prefer more intense themes. They are some of the results of a huge studio with almost 800 million of songs heard by a million people on Spotify. Although these data may seem logical, there are others more intriguing: the Boys like pieces more animated than the girls, but that difference in gender is invested in the two hemispheres of the planet. Or, the divergences of intensity are reduced as we approach the equator. That's the rhythm of the planet.

Researchers at Cornell University (USA) have had the rare opportunity to study an immense database of the Spotify music service (one of the authors of the studio works in the company). They counted with 765 million of selected songs (i.e., chosen by the user and not random) by a million customers of the service from all over the world. Taking advantage of that each song carries a series of metadata with 11 characteristics (rhythm, if it is sung or instrumental, tempo, if it is danceable, acoustic or electronic, Valencia...) They were able to measure the musical intensity of each song and that of all the songs.

They checked so there are a number of universal patterns. They observed, for example, that humans hear more animated music between eight in the morning and eight in the afternoon, with a low mood between three and four in the morning. They did not see, however, significant variations during the day. Something that did have detected previous studies that used tools like Twitter messages to press the planetary rhythm. They also saw how the week is cheering up to what the Cure sang in his Friday I'm in Love: Friday, followed by Saturday, are the days when we hear the music more exciting. On Sundays and Mondays, at least.

Friday is the most musical day and the peak in intensity is reached the days after the summer solstice

"A posteriori, many of the patterns that we have found may seem logical," says the director of Cornell's Social Dynamics laboratory, Michael Macy, professor of sociology and co-author of the study. "But it's important to confirm our intuitions with empirical data and the patterns we've seen are based on a unique database of listening habits in 51 countries around the world," he adds. Among these logical patterns would be the fact that the maximum of musical intensity occurs during the summer solstice from a minimum reached in the winter months. It also seems to be expected that the intensity score of the music consumed by children under the age of 18 is more than twice that of the older than 50 years. But there are other apparently not so logical results.

800 millones de canciones para oír el ritmo del planeta

"One of the most striking results is the difference in gender patterns between the northern hemisphere and the southern hemisphere," says Macy. Although on the global average, boys listen to music more animated than girls, "in the Northern Hemisphere, women hear music with less intensity, especially at night, while in the southern hemisphere is the opposite: women choose music more intensely than that which men prefer, "he adds. The authors of the study, published in Nature Human Behaviour, do not analyse the possible causes of these differences, although they point to a possible cultural basis.

"It was also an unexpected thing that the music played in Latin America is relatively more intense and the heard in Asia more relaxed compared to Oceania, Europe or North America," recalls the researcher and principal author of the study Minsu Park. "I think the last three regions are culturally similar and the results suggest that there might be cultural differences in preferences for external stimuli, such as different levels of musical intensity," adds Macy's pupil.

There is a striking gender difference: while the Northern Hemisphere girls prefer quieter subjects, in the South they overcome in animated themes to the boys

For what they do not have explanation, although they could intervene environmental factors, it is for the most surprising fact of all: in all the metrics where they detected differences (even in the differences of age, although to a lesser extent) these were reduced as they were approached the equator. For example, it is from this imaginary line where gender differences are invested. Park recognizes that it's something they'll have to investigate.

The authors recognize that the design of the study can introduce some bias. For example, the sample is made up of users of the Spotify payment version. Besides, they have no data from Africa. The study was conducted between January and December 2016, when this musical service had not yet been deployed in too many African countries. They still consider it a good basis for the study of human behaviors.

"Much of the social science research done in the US is about the behavior of Americans, sometimes with the tacit assumption that the results are generalizable to other cultures. Data from global social platforms such as Spotify, Twitter and Facebook offer a much needed opportunity to address intercultural and transregional differences in human behavior, "reasons Professor Macy. Moreover, he adds, "It is also very difficult to observe people's emotions at the population level and we know that what they say about their emotions can be unreliable (we tend to put our best face). These data allow to observe the real human behavior, not only the self-reports of the people on their behavior ".

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