Washington (AFP)

Where does the pleasure come from? A clever mix of uncertainty and surprise, say researchers who have gutted a machine hundreds of tubes to discover the secrets.

The team of researchers analyzed statistically thousands of chord sequences (without melodies and lyrics), taken from 745 American Billboard pop hits from 1958 to 1991, including "Ob-La-Di, Ob-La- Da "Beatles," Red Red Wine "by UB40 and" Knowing Me, Know You "by ABBA.

"It's fascinating that humans get pleasure from listening to a song only because of the order of the sounds," says Vincent Cheung of the Max Planck Institute for Cognitive and Brain Sciences at AFP Germany, which led the study published Thursday in the journal Current Biology.

A machine learning algorithm quantified the level of uncertainty and surprise of 80,000 chord suites, and then had about 80 humans listen to a selection of songs while they were in an MRI scanner. that researchers are watching their brains.

Scientists have observed that when participants were relatively sure about the next agreement, they would have fun if the following agreement were a surprise.

And when they were unsure what to do next ... they had fun when the deal was not surprising.

To gauge expectations and feelings, scientists observed the corresponding brain regions.

Only the chords, and not the melodies and the lyrics, were played because otherwise they would have risked arousing more or less pleasant memories for the listeners, and contaminating the experience.

Could this data one day help a composer to find the magic formula for a tube?

"It could be an important element to exploit, but it could not be the only thing to create a pop song", replies Vincent Cheung humbly.

In the course of the experiment, the most noted chord sequence of the participants was "Invisible Touch", by Genesis, in 1980.

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