A young chimp called Sakura replays pleasant tunes that she likes more often than those she doesn't
Chimpanzees are biologically programmed to appreciate pleasant music.
The discovery comes from experiments showing that an infant chimpanzee prefers to listen to consonant music over dissonant music.
That suggests the apes are born with an innate appreciation of pleasant sounds, say scientists in the journal Primates.
Until now, this was thought to be a universal human trait, but the new finding suggests it evolved in the ancestors of humans and modern apes.
Tasuku Sugimoto and Kazuhide Hashiya of Kyushu University in Hakozaki and colleagues in Japan tested how a young captive chimpanzee named Sakura responded to music as she aged from 17 weeks to 23 weeks old.
Sakura had been been abandoned by her mother, forcing members of the staff at Itozu-no-mori Park in Fukuoka where she lived to care for her.
One of the major factors that constitute musical appreciation might not be unique to humans
Japanese researchers outline their discovery in the journal Primates
Crucially, she had never been exposed to any form of music before she took part in the trials.
During the experiments, Sakura lay on a bed while a woollen string was attached to her right hand, allowing the infant chimp to pull on the cord at will.
A music player and speakers was then set up around her, playing melodies lasting between 38 and 63 seconds long. Every time Sakura pulled on the cord, the music would be repeated.
During six trials, conducted one a week for six weeks with each lasting around 20 minutes, the researchers played Sakura a range of tunes.
One was a 38 second minuet from Duette Englischer Meister in F major. Another, a 38 second minuet from a handwritten sheet of German music composed in 1720.
These consonant tunes were also adjusted using orchestration software to make them dissonant. For example, all the Gs in the 38 second Duette Englischer Meister music were altered to G-flat and all the Cs to C-flat, creating 32 dissonant intervals.
In three of the six trials, the researchers first played Sakura the more pleasant consonant music and in the others, they started with the less pleasant sounding dissonant music.
Play it again
Across all six sessions, Sakura pulled on the cord to voluntarily listen to the pleasurable music significantly more often than to the dissonant passages.
"Our main surprise was the results being so consistent," says Hashiya. "She rapidly learnt the rule of the setup and consistently produced consonant music over dissonant music for longer duration."
The discovery that an infant chimp, with no prior exposure to music, innately prefers to listen to consonant melodies could have important implications for how an appreciation for music evolved.
"Music is one of the universal human natures beyond cultures, just like language," says Hashiya.
But it was always thought that it was a uniquely human trait, one present even in babies just a few days old.
"The preference for consonant music over dissonant music in an infant chimpanzee has implications for the debate surrounding human uniqueness in the capacity for music appreciation," the researchers write in Primates.
Bored by what they're hearing?
Experiments have shown that various bird species can differentiate between consonant and dissonant sounds, but they do not actively prefer listening to one over the other.
Other research on cotton-top tamarin monkeys also found no such preference.
But Sakura's appreciation for consonant melodies "specifically suggests that one of the major factors that constitute musical appreciation might not be unique to humans: instead it might be something that we share with our phylogenetically closest relatives," say the researchers.
Hashiya explains that it is very difficult to rule out whether young human infants have had prior exposure to music on the radio or in their family's house before they are tested.
"To figure out the response of Sakura, we have to consider her lack of music experience, which should draw a clear contrast with ordinary human infants. It supports the view that the preference is independent of cultural experience," he says.
The researchers hope to study the effect further.
For now they speculate that the chimps' innate preference for pleasurable melodies may serve some biological function in the wild, perhaps helping them detect other chimps' voices above other sounds, for example.