Humans can identify emotions in the sounds made by different mammals, reptiles and amphibians, according to a study which suggests that there may be a universal code for the vocal expression of feelings in the animal kingdom.
Amphibians, reptiles, mammals - all of them communicate via acoustic signals. Researchers from Vrije Universiteit Brussel in Belgium and Ruhr-Universitat Bochum in Germany showed that humans are able to assess the emotional value of these signals.
The findings show that there might be a universal code for the vocal expression and perception of emotions among animals. Previous studies had demonstrated that humans are capable of identifying emotions in the voices of different mammals. The new study results have been expanded to include amphibians and reptiles.
Participants in the study included 75 individuals whose native language was English, German or Mandarin.
They listened to audio recordings of nine different species of land-living vertebrates in the classes mammals, amphibians and reptiles. Participants were able to distinguish between high and low levels of arousal in the acoustic signals of all animal classes. To do so, they mainly relied on frequency-related parameters in the signal.
"The findings suggest that fundamental mechanisms for the acoustic expression of emotions exist across all classes of vertebrates," researchers said.
"The evolutionary roots of this signal system might be shared by all vocalising vertebrates," they said. The finding goes in the direction of what Charles Darwin suggested more than a century ago, namely that acoustic expressions of emotion can be traced back to our earliest land-dwelling ancestors, they added. The findings were published in the journal Proceedings of the Royal Society B.
