You probably agree with the animals on which bird calls, frog noises and cricket chirps are most attractive – new research

Animals do all sorts of things to attract each other as potential mates. Many birds, for example, produce feathers with elaborate color patterns – from the iridescent plumage of many hummingbirds to the famous shiny tail of a peacock. Charles Darwin, an early pioneer of the theory of evolution, saw these colors and concluded that they exist because other birds find them attractive.

But this raised a particular question: why did Darwin himself find these colors beautiful too?

Indeed, he noted that some animals have “almost the same taste for beauty as we do,” a simple observation with radical implications. Our sense of beauty might be something we humans share with other animals, rooted in biology.

More than a century after Darwin made his observations, my colleagues and I decided to test this idea.

I am an expert in animal communication, with a focus on sound production and perception. I have worked with species such as zebra finches, fringed bats and tungara frogs. For example, late at night in Panama, I watched remote video feeds of female túngara frogs as they listened to calls I broadcast from different speakers. Eventually, a woman will jump to a speaker, revealing which of the calls she prefers.

Could it really be possible that this little frog and I are attracted to some of the same sounds? What might shared preferences say about what animals and humans have in common? We needed data to find out.

Global experience

To properly test Darwin’s idea, we needed two things: a large collection of animal sounds already tested on animals, and a large number of human listeners willing to give feedback.

For the sounds, we relied on decades of published research, including some of our own as well as studies by generous colleagues who let us use their recordings. We ended up with 110 pairs of sounds from 16 different species, including frogs, insects, birds and mammals. In each pair, sounds are used to attract potential mates; scientists had already found which of the two versions animals tended to prefer.

For human listeners, we created a fun online experience played by over 4,000 participants from around the world. The task was quite simple: we played each pair of sounds in random order, then asked which one the human participant preferred.

What we found

The results were striking. In our data set, including animals separated from humans by hundreds of millions of years of evolution, people tended to agree with animals about which sound was more pleasant.

Surprisingly, the stronger the animal’s preference, the more likely humans were to agree. We also found that people were noticeably quicker to click or tap the sound that the animals found most appealing, suggesting a subconscious aspect to these preferences.

Song sparrows and humans tend to prefer this song. Stephen Nowicki and Susan Peters27 KB (download)

Song sparrows and humans tend not to prefer this song. Stephen Nowicki and Susan Peters41.8 KB (download)

People were particularly in agreement with animals when it came to what researchers call “ornaments”: the trills, chucks, clicks, and extra flourishes that animals can add to their calls. These sounds were more appealing to both animal and human listeners.

Why do we share these preferences?

This is a key question, and many more studies will be needed to piece it together. Our current work suggests that the architecture of the nervous system may help determine shared preferences. Despite the enormous diversity of life on Earth, many basic structures of sensory systems are similar across species. Shared mechanisms of sound perception may lead to shared biases in sound preference.

We also found many factors that did not suggest a deal. Participants with expertise in animal sounds or highly skilled musicians were no different from other human judges. Interestingly, those who reported spending more time listening to music daily were more supportive of animals, a surprising finding worth investigating.

Hourglass tree frogs and humans tend to prefer this call. Martin J Fouquette Jr10.3 KB (download)

Hourglass tree frogs and humans tend not to prefer this call. Martin J Fouquette Jr5.22 KB (download)

More to investigate

We focused on sound, whereas Darwin’s original observation was about color and visual beauty. Do humans also share visual preferences with animals? And the sense of smell? And what happens in our brains when we make these instant aesthetic judgments? Are the same neural circuits at work when a human and a frog both choose the same call?

Preferences in animals are often subtle and variable across individuals and populations. I would love to ask birds what they think of different frog calls and vice versa, but only humans can we directly ask such questions.

We also discovered cases where humans disagreed with animals. Our results show a trend, not a rule, and understanding where this variation comes from will be fascinating to discover.

My favorite takeaway from this research is a simple reminder.

People find so much beauty in nature, from the dazzling colors of butterflies to the melodious songs of birds and the aromas of flowers. Yet all of these evolved to attract other species, not us. Perhaps it’s because we humans share something fundamental with other animals that we also find beautiful.

This article is republished from The Conversation, an independent, nonprofit news organization that brings you trusted facts and analysis to help you make sense of our complex world. It was written by: Logan S. James, The University of Texas at Austin; McGill University

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Logan S. James is affiliated with the Earth Species Project.