When leaving my apartment, I make sure to leave the radio on for my cat. I like to think the songs are a satisfactory substitute for the voices that fill the apartment when people are home. Then again, perhaps the music is nothing more than a nuisance to my feline friend.

“It’s something that people have wanted to know for a long time,” says Pralle Kriengwatana, an affiliate researcher at the University of Glasgow’s School of Biodiversity, One Health and Veterinary Medicine. “And there are more and more studies on it.”

But by and large, she says, those studies have focused on one simple question — what effect does music have on non-human animals? — without taking into consideration how or why these effects come about. 

In a paper published in Applied Animal Behaviour Science last year, Kriengwatana and her colleagues propose an alternative research framework. It first asks what animals actually hear when exposed to music, then applies this to specific welfare goals.

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Do Animals Understand Music?

Though we don’t yet have the technology to monitor the brain activity of a freely moving animal, admits Kriengwatana, researchers can turn to behavioral tests instead. 

In her own work, she may train a bird to peck on, say, its right side if it perceives a sound pattern as regular — versus its left side if it perceives the sound as irregular. In that way, we can slowly piece together which elements of music that an animal is responding to.

Similar tasks enable researchers to piece together the range of pitches than an animal can hear. Not every creature is up to the task, however. Sometimes, a test subject can’t quite figure out what a researcher is asking for; other times, it’s truly unable to recognize a sound.

“If you play an animal a sound that isn’t within its range, of course it isn’t going to respond,” Kriengwatana says. “[Rats] can only hear the highest frequencies in Mozart, so are they actually hearing Mozart?”

But don’t blame the rats. All animals’ brains and sensory systems (including ours) are naturally attuned to the sounds that are most meaningful to them. These may include the sounds that an animal uses to communicate with others of its kind — or the growls a predator makes.

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How to Tell If Music Affects Animal Behavior

For species that do respond positively to musical cues, it’s up to researchers to determine the mechanisms at work within their minds. There are currently three main lines of reasoning, Kriengwatana says.

Sound Masking

The first, which researchers call “acoustic masking,” argues that music improves welfare by blocking out sounds that are more stressful for animals.

An animal shelter that Kriengwatana’s friend works at, for example, “is loud and the dogs are constantly barking,” she says. But a handful of studies have shown that music can reduce barking and other physical indicators of anxiety in this stressful setting.

Non-musical sounds, like white noise, can be helpful, too.

But be warned, notes Kriengwatana, that not all acoustic masking is inherently good. When meaningful sounds such as whale song, for example, are blocked by anthropogenic noise pollution, this can be incredibly harmful.

Sensory Stimulation

The second hypothesis deals with sensory stimulation: It states that music improves welfare because it boosts the complexity of an animal’s environment, though not all genres of music are perfect for every environment. 

Calming music may benefit rowdy dogs at a shelter, while lab rats benefit from something a bit more stimulating. And sometimes, if an animal is already overstimulated — say, by visitors constantly tapping on its enclosure at the zoo — it may not desire any additional sound.

Arousal Modulation

The last hypothesis, which researchers call “arousal modulation,” argues that music improves welfare by influencing emotions. Some animals have been studied so much — or are simply so close to humans — that we can make a relatively educated guess about how they’re feeling. 

“We know that, for example, when dogs are happy, they wag their tails,” Kriengwatana says.

But for creatures that are more distant from us and lack many shared behaviors, interpretation becomes more difficult. Certain physiological tests, says Kriengwatana, can tell how “activated” an animal’s body is by measuring things like heart rate and blood pressure. 

Still, she continues, it’s difficult to know whether the animal is activated because it finds the music appealing or because it finds the music scary and wants to flee.

Do Animals Enjoy Music?

How do we know if animals enjoy music? In some scenarios, researchers can simply ask animals like chimpanzees which of the several musical options they prefer. But even species unable to directly communicate with us can display music preferences by, say, working harder to overcome obstacles and access certain sounds.

“For us, music has a special place in our hearts. We really revere it in many ways. It’s healing. It’s bonding. It’s emotional,” Kriengwatana says, adding that we expect non-human animals to feel the same way.

But it’s far more nuanced than that: Our appreciation, she says, comes from a very personal combination of both biology and culture. And if researchers don’t take these biases into consideration, then music research itself will also be tainted with bias.

“The field really needs to work together with people from the humanities and people who study music to understand what biases we have and what music is to us,” Kriengwatana says. “From there, we can ask much more interesting questions.”

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