Researchers used a machine learning model to mathematically analyze 80,000 chords in 745 classic U.S. Billboard pop songs. Other elements such as lyrics and melody were stripped out for the analysis.
When listeners were relatively certain about what chord to expect next, they found it pleasant when they were surprised by an unexpected chord, and when they were uncertain about the next chord, they found it pleasant when subsequent chords weren't surprising.
"It is fascinating that humans can derive pleasure from a piece of music just by how sounds are ordered over time," said study author Vincent Cheung, from the Max Planck Institute for Human Cognitive and Brain Sciences, in Germany.
"Songs that we find pleasant are likely those which strike a good balance between knowing what is going to happen next and surprising us with something we did not expect. Understanding how music activates our pleasure system in the brain could explain why listening to music might help us feel better when we are feeling blue," Cheung said.
The study was published Nov. 7 in the journal Current Biology.
Study co-author Stefan Koelsch, from the University of Bergen, in Norway, said, "Although composers know it intuitively, the process behind how expectancy in music elicits pleasure was still unknown. One important reason was that most studies in the past only looked at the effects of surprise on pleasure but not the uncertainty of the listeners' predictions."
The effect of uncertainty and surprise on one's appreciation for other art forms, such as dance and film, could be subjects for future research, the researchers added in a journal news release.