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Whether it’s classical, pop, jazz, or hip-hop, almost everyone likes some form of music. But our appreciation of rhythm and rhyme might not be unique.

Decades of research have hinted that animals may also be music lovers. And further study of how different species respond to music may help us to understand how, and why, the ability to perceive and appreciate music evolved in us. There’s no doubt that, to us, music is different from other sounds, you know it when you hear it.

That ‘musical sense’ is called musicality. And it seems that even animals very, very distantly related to us have it, too. One group of intrepid researchers tested whether Nile crocodiles could tell the difference between music and simple sounds.

They used a brain imaging technique called functional magnetic resonance imaging or fMRI, which uses the blood flow in different areas of the brain to estimate activity. Now, if you’re wondering how you get a crocodile to kindly sit in a big ole machine while you scan its brain, well, these were juveniles less than a meter long. They were also lightly sedated and wearing a special helmet so they didn’t move their heads too much.

And incredibly, the researchers did see different patterns of brain activity when the crocodiles listened to Bach as opposed to random chords, suggesting the music sounded different to them. And many animals can go a step further and actually distinguish between different genres of music. Pigeons can be trained to peck one key if they hear an organ piece by Bach and a different key if they hear an orchestral piece by Stravinsky.

And even fish can tell blues from Bach. Apparently everyone likes testing with Bach. But this doesn’t tell us whether or not they actually like music.

To get at that, researchers have looked more closely at how animals react to melodies and beats. In one study, scientists actually created music specifically for cats by using sliding frequencies, a common feature of cat vocalizations, and setting the tempo to the same number of beats per minute as purring. The cats were more likely to turn towards and approach speakers which were playing the special cat music than those playing regular music, suggesting they preferred the feline remix.

And just like us, animals seem to find some types of music more relaxing than others. For example, a 2012 study found 117 kenneled dogs slept more and spent less time barking when played classical music. Heavy metal, on the other hand, seemed to make them more anxious.

And studies in primates, elephants, birds, and rodents have all found that at least some kinds of music can chill them out, promote social activities like grooming, or reduce nervous or aggressive behaviors. But being relaxed by something doesn’t necessarily mean you enjoy it. Perhaps the most convincing evidence that animals actually like music comes from studies that let them freely choose what to listen to.

In a 2007 study, when monkeys were allowed to pick between different types of music by moving to different parts of a chamber, they chose lullabies over techno. But if given the option, they preferred silence. That led researchers to conclude that our relatives just don’t like music.

But some scientists have since pointed out that most studies use Western genres, and there are a lot of other types of music out there. So in a 2014 study, researchers played three kinds of international music just outside of a large chimpanzee enclosure. The 16 study chimps apparently liked West African akan music and North Indian raga music, spending much more time near the speaker when they were playing.

But they were pretty lukewarm about Japanese taiko music, it was a toss up between that and silence. Taken together, the science suggests that animals, especially mammals, do have some musical preferences. But why do animals like music at all?

The answer to that is still a bit of a mystery. In fact, we don’t even really know why humans like music! Scientists have a lot of theories about the evolution of musicality.

Some think that musicality may be related to our time in the womb. The idea is that we like steady beats and vocalizations because they remind us of our mother’s heartbeat and her voice. This would perhaps explain music preference in mammals, but it’s less of a satisfying answer for the egg-laying groups like birds.

So other researchers think it might have more to do with the importance of understanding vocalizations. Early humans may have used music-like calls to communicate, so being better able to understand the meaning of calls by picking up on subtleties in tone and rhythm could have increased a person’s odds of survival. And that could even explain why we find music pleasurable, since our brain’s reward system is all about promoting things that keep us alive and reproducing.

This hypothesis would also explain why primates and birds have musicality, they also communicate with vocalizations a lot. And it might even mean there are musical preferences throughout the animal kingdom. After all, there are species of fish and even insects that communicate with sound.

But ultimately, the origins of our love of music may remain a mystery, as such hypotheses are difficult to test empirically. Fortunately, we don’t have to know why musical enjoyment evolved in humans, or in our furry and feathered friends, to be able to rock out together. Thanks for watching this episode of SciShow!

If you want to better understand why we like certain kinds of music, you might want to check out our episode on why we prefer some combinations of notes over others. [♪ OUTRO].