New research not only supports Darwin’s views, but also identifies a universal “language” of arousal emitted and understood by amphibians, reptiles, birds, and mammals. The findings, published in the journal Proceedings of the Royal Society B, suggest that we are at least somewhat like the famous fictional character Doctor Dolittle, who could decipher animal communications with ease.
“Our study shows that humans are naturally able to recognize emotional arousal across all classes of vocalizing animals,” said lead author Piera Filippi, a postdoctoral researcher at the University of Aix-Marseille and the Max Planck Institute for Psycholinguistics. “This outcome may find an important application in animal welfare, suggesting that humans may rely on their intuition to assess when animals are stressed.”
Prior research additionally suggests that animals understand human emotional vocal expressions. Pet owners are often more attuned to this, given the reactions that dogs, cats, horses, birds, rodents, and more have to a range of owner outbursts, from angry scolding to happy praise.
For the latest study, Filippi, senior author Onur Gunturkun, and their team went beyond investigating such a familiar collection of animal pets. They instead gathered 180 recordings of vocalizations from nine different and very diverse species: hourglass treefrog, black-capped chickadee, common raven, American alligator, African bush elephant, giant panda, domestic pig, and Barbary macaque. People who spoke English, Mandarin, and German were then recruited to evaluate the levels of arousal communicated in each animal recording.
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The human listeners, no matter their native language, aced the tests. This indicates that human ability to assess vocal expressions of arousal — whether emitted due to sexual bliss, infant distress, or terror over a predator — is biologically rooted and somehow cemented in our DNA.
The scientists further conducted an acoustic analysis of the recordings. Pairing this data with the findings concerning the human listeners, the researchers discovered that people use multiple acoustic parameters to infer levels of arousal in vocalizations. Mainly, however, humans rely on fundamental frequency cues and the forcefulness of the sounds.
The primary explanation for the ability, seemingly shared across much of the animal kingdom, has to do with the body-sound connection.
“Across vocalizing animals, higher levels of emotional intensity may induce the contraction of muscles that are required for vocal production,” Filippi explained. “This modification alters the quality of the sounds produced, often resulting in changes related to the perceived frequency of the sound.”