This extensive collaborative research effort, involving the Smithsonian Tropical Research Institute (STRI) alongside teams from the United States, Canada, and New Zealand, utilized an innovative approach to explore how human auditory perception aligns with that of various animal species. Through an experimental online game engaging over 4,000 worldwide participants, researchers presented pairs of animal sounds from 16 different species spanning a broad spectrum of the animal kingdom. Participants were asked to select which sound they preferred, enabling a large-scale comparison of subjective preferences between humans and animals previously studied for their own acoustic inclinations.

The study’s genesis traces back to seminal work from the early 1980s by A. Stanley Rand and Michael J. Ryan, when they first documented the vocal preferences of female túngara frogs in Central American rainforests. Their pioneering research demonstrated that female frogs exhibited a marked preference for males emitting more complex calls, highlighting the role of acoustic intricacy in mate selection. Building on this foundation, Ryan and colleagues sought to determine whether humans would exhibit similar preferences to those demonstrated by animal females, especially for complex and ornamented sounds used in mating calls.

Logan James, the lead author and STRI research associate, expressed a deep fascination with uncovering the origins of these cross-species auditory preferences. He pointed to earlier findings that not only the intended female receivers but also unintended listeners or “eavesdroppers,” such as parasitic flies and predatory bats, showed preferences for complex calls. This revelation spurred interest in whether such acoustic tastes are widespread across taxa and whether humans might share in these sensory biases.

Human participants engaged via a gamified citizen science platform designed not just for data collection but for participant enjoyment and broad accessibility. This method allowed researchers to gather a vast, diverse dataset examining human choices across an array of animal vocalizations. By focusing on sounds for which animal preferences had already been experimentally established, the team was able to assess the extent of alignment between human and animal auditory preferences systematically.

The results were compelling. Researchers observed a considerable overlap in acoustic preferences, with humans more often favoring the same calls that animals themselves preferred. Interestingly, the degree of concordance between human and animal choices correlated with the strength of the animals’ preferences: the more pronounced the animal’s choice for a particular sound, the more likely humans were to select that sound as well. Furthermore, reaction times indicated that humans made quicker choices when selecting the sounds deemed more attractive by animals, suggesting an innate or intuitive recognition of acoustic appeal.

Among the acoustic features most consistently preferred were lower-frequency sounds, which correspond to lower pitch ranges, and complex acoustic embellishments such as trills, clicks, and “chucks” — ornamental modulations that likely serve to enhance signal attractiveness or convey fitness. These auditory characteristics are believed to tap into shared sensory processing strategies that have evolved among diverse vertebrates, including humans, to detect and respond to biologically relevant sounds.

Michael J. Ryan underscored the significance of these findings through the lens of evolutionary biology, referencing Charles Darwin’s early insights. Darwin had noted animals’ tendency to display a “taste for the beautiful,” an aesthetic sense that sometimes parallels human preferences. The study’s evidence that human and non-human animal preferences converge on common acoustic themes lends empirical weight to Darwin’s observation, implying shared neural and sensory mechanisms underpinning auditory appreciation across species.

This shared auditory preference also suggests a deeper evolutionary basis for signal design in animal communication. It indicates that certain features of animal calls may have been shaped not only by selection pressures within species but also by broader sensory biases extant in receivers, including humans. Such biases might drive the evolution of calls that exploit universal perceptual proclivities, contributing to the emergence of complex communication systems and influencing mate choice dynamics.

Moreover, the study expands the methodological toolkit for cross-species analyses of sensory preferences by demonstrating the efficacy of online, gamified citizen science. This approach facilitates large-scale data gathering from a heterogeneous human population, enhancing the ecological validity and generalizability of findings. It opens pathways for future inquiries into the comparative cognition of sensory perception, bridging human psychology with animal behavioral ecology.

At the same time, this research underscores that human sensory systems do not exist in isolation but share evolutionary continuity with other animals. The interplay between biological function and aesthetic appreciation in acoustic signaling highlights the universality of certain perceptual mechanisms that transcend species boundaries, enriching our understanding of the natural world and the evolutionary origins of auditory beauty.

In summary, these findings affirm that humans and animals are attuned to similar acoustic signals, especially those featuring low-frequency components and elaborate ornamental elements. They reveal that the human sense of sound beauty is deeply rooted in evolutionary history and shared sensory neurobiology. The implications extend beyond the scientific community, inviting broader reflections on the interconnectedness of life, the nature of sensory experience, and the evolutionary conservation of beauty in communication.

Subject of Research: People

Article Title: Humans share acoustic preferences with other animals

News Publication Date: 19-Mar-2026

Web References:

• DOI link
• The Music Lab online game

Image Credits: Credit: Raina Fan

Keywords: Evolutionary psychology, Psychological science, Behavioral ecology, Animal communication, Ethology, Cognitive psychology

Fringe-lipped bats (Trachops cirrhosus) stand out in the annals of animal behavior for their skillful eavesdropping on the vocal signals of over a dozen sympatric frog and toad species. These calls, primarily evolved as sexual advertisements conveying location and fitness to potential mates, inadvertently serve as auditory beacons for bats seeking their next meal. Previous research established that adult fringe-lipped bats discern between palatable and toxic or otherwise unprofitable amphibians, but the ontogeny—the developmental trajectory—of this sophisticated auditory discrimination had remained elusive until now.

Researchers developed an experimental framework involving wild-caught juvenile and adult bats exposed to playback recordings of 15 local frog and toad species’ mating calls. The spectrum of these calls included signals from species that differ significantly in palatability—ranging from harmless and nutritious, to toxic, to those too large to handle. The controlled acoustic environment allowed the scientists to meticulously measure behavioral responses such as approach frequency and intensity, key indicators of predation motivation and decision-making processes.

The results underscore a striking developmental dissociation. Adult bats robustly differentiated calls of palatable prey from those signaling unpalatable or dangerous species, preferentially approaching the former. In contrast, juveniles lacked this nuanced discrimination, responding indiscriminately to both edible and toxic prey calls. Intriguingly, juvenile bats showed an early ability to assess prey size acoustically, avoiding calls from larger species beyond their handling capability, illustrating that body-size assessment develops prior to palatability recognition.

This developmental progression reveals the particular importance of experience in shaping foraging decisions. Juvenile bats likely encounter the costs of erroneous prey choice—such as ingesting toxins or injuries inflicted by oversized amphibians—during an extended trial-and-error learning phase. Over time, sensory association between particular acoustic signatures and adverse post-ingestive consequences refines their predatory acuity, effectively calibrating the bat’s auditory “caller ID” to the risks and rewards of the environment.

Beyond the fascinating behavioral dynamics lies a broader ecological and evolutionary context: the bats’ ability to eavesdrop on an unrelated species’ mating signals provides a compelling example of interspecific communication networks influencing natural selection. The acoustic signals produced by frogs, while primarily for intraspecific mating communication, inadvertently mediate predator-prey interactions. Such eavesdropping imposes selective pressures on signal design—a delicate balance between attracting mates and avoiding deadly predators.

Moreover, STRI’s findings emphasize the role of neural plasticity during critical developmental windows for sensory and cognitive functions in wild animals. Like human children who learn to differentiate social cues and dangers through experience, juvenile fringe-lipped bats must accumulate environmental data to fine-tune their responses to complex auditory stimuli. This highlights an adaptive strategy allowing flexibility in dynamic ecological landscapes where prey communities and predation risks can vary spatially and temporally.

Technically, the study utilized a battery of playback experiments wherein acoustic stimuli, standardized for intensity and fidelity, simulated natural call sequences from single males and large choruses of túngara frogs (Engystomops pustulosus). Behavioral metrics were quantified through video recordings and real-time observations, providing robust datasets to distinguish age-related differences in auditory-guided predation choices. The research also employed cross-validation with known palatability and toxicity profiles to cement links between behavioral responses and prey characteristics.

Additionally, the experiments shed light on the bats’ neural mechanisms for processing complex acoustic signals that feature dynamic spectral and temporal patterns. The intricate whine-plus-chuck call of the túngara frog, for instance, exemplifies a multimodal signal encoding species identity and mate quality. The ability of fringe-lipped bats to parse and react differentially to these calls indicates sophisticated auditory discrimination at neural circuitry levels, potentially involving both innate predispositions and learned associations.

Overall, this landmark research propels forward our understanding of predator-prey interactions mediated through sensory eavesdropping and learning. It invites further exploration of similar ontogenetic patterns in auditory discrimination across other taxa, highlighting the critical integration of experience, neuroethology, and ecological pressures. These insights not only enrich basic science but may also inform conservation efforts by elucidating the sensory ecology fundamental to species survival in increasingly disturbed tropical habitats.

In an era marked by rapid habitat transformation and biodiversity loss, recognizing the nuanced relationships between species and the emergent behavioral adaptations driven by sensory environments offers a pathway to more informed ecosystem management. The work of STRI researchers exemplifies the power of interdisciplinary field and laboratory research to decode the complex life histories unfolding in nature’s acoustic landscapes.

Subject of Research: Animals
Article Title: The Ontogeny of Decision-Making in an Eavesdropping Predator
News Publication Date: 29-Apr-2025
Web References: https://royalsocietypublishing.org/doi/10.1098/rspb.2025.0450
Image Credits: Credit: (c) Joseph See
Keywords: Animal research, Animal science, Behavioral ecology, Ethology, Ecology, Predation, Ecosystems, Neuroethology, Ecological dynamics

“Bone is a dynamic tissue that responds to external stimuli, so changes in bone structure provide great clues about where and how a person lived and died,” Smith-Guzmán said. “When I looked at an additional 125 skulls from nine burial sites across Panama, I found seven cases of surfers’ ear in males and one in a female skull, all from sites near the Gulf of Panama.”

No one really understands exactly how the bony growths, technically called exostoses, form. But the skin is thin in the ear canal and the accepted theory is that cold water or cold temperatures caused by wind and water make the bone react by growing extra layers, similar to the way bone spurs form on the feet and in other places where there is constant irritation or stress. Almost half of the members of a swimming club in England had surfer’s ear according to a report cited in the study.

Unlike most tropical countries where seawater is warm, water temperature in the Gulf of Panama plummets between January and April when strong trade winds from the north force warm surface water out into the Pacific and colder, deep water rises to the surface to replace it. This deep, nutrient-rich water feeds tiny sea organisms, which in turn are eaten by fish and whales. The Gulf becomes an extraordinarily productive fishing ground supporting a thriving fishing industry and attracting dolphins, sharks and other top-of-the-food-chain animals.

Years ago, when co-author Richard Cooke, zooarchaeologist at STRI, unearthed a male skeleton with surfer’s ear in Sitio Sierra, near Aguadulce in Panama, he was a STRI post-doctoral student with only rudimentary knowledge of physical anthropology. But he collected all of the human remains he found, enabling Nicole-Smith Guzmán to reexamine them 43 years later.

Cooke spent much of his career studying ancient fishing practices. He found that Panama’s pre-Columbian peoples fished from boats all along both the Pacific and Caribbean coasts of Panama. If fishing alone put people at higher risk for surfer’s ear, then more cases of the bony growth would be present at all of the sites, but all of the examples came from areas near the Gulf.

“We think it more likely that diving in the cold waters of the Gulf caused these cases of surfer’s ear,” Smith-Guzmán said. “Silvery mother-of-pearl ornaments, and orange and purple ones from two large ‘thorny’ oysters in the Spondylus genus were common in burials and comprised an important trade item in the region. Some of these shells wash up on beaches, but by the time Vasco Nuñez de Balboa and other Spanish explorers arrived, their chronicles tell us that expert divers were trained from childhood to dive down to four fathoms to retrieve pearl oysters of desirable large size.”

The Spanish encouraged this industry and for many years, Panama was known for its pirates and pearls, including La Peregrina, the largest pearl known at the time it was found.

The team also ruled out fungal or bacterial ear infections common in the tropics that sometimes cause bone deformations: most of the skulls affected were from males, and infections should occur in both male and females at about the same rate. From the evidence they have so far, it looks like mostly males were involved in whatever activity caused surfer’s ear in Panama. In another study, archaeologists in the Canary Islands found roughly equal numbers of cases of surfer’s ear in ancient male and female skulls, suggesting that aquatic activities there were not restricted to one gender.

“I spoke to one ear, nose and throat specialist in Panama and she has never seen a case of surfer’s ear here, but we want to do a follow-up study in which we look at skulls from a much wider area and also do a survey of doctors in Panama to find out if surfers or divers ever show up with surfer’s ear these days,” Smith-Guzmán said.

Surfer’s ear is an intriguing subject that archaeologists, anthropologists and medical doctors have explored for more than a century. Although the exact causes of this phenomenon is still debated, these bony growths offer important clues into the cultural activities, gendered division of labor and environmental conditions in the past.

Surfer’s ear points to ancient pearl divers in Panama
Smithsonian Tropical Research Institute

Journal
American Journal of Physical Anthropology
Funder
Smithsonian Tropical Research Institute
DOI
10.1002/ajpa.23757