Animal Language: Is there a universal code?

We recognize excitement even on reptiles, frogs or birds

We understand animals much better than we think: An experiment proves, that humans are instinctively able to identify emotions of various animal species. Pitch and sound of the animal voice tell us if the frog, dog or bird is relaxed or excited. This could indicate, that there is something like a universal code in expression of feelings known to every tetrapod, according to scientists.

If our dog is sad, relaxed or happy we realize it immediately - and on the other side the animal is able to read off our voice regarding how we feel. This works with apes, horses, cats and other mammals, at least regarding our basic feeling.

Instinctive understanding?

But how does this look like with animals that are not that tightly related to us, like lizards, frogs or birds?

For more than a decade, Charles Darwin has hypothesized, that the vocal expression of emotions goes back til our earliest terrestrial ancestors.

Piera Filippi and his colleagues of the University of Brussels explain. But this would mean, that all vertebrates understand a kind of universal code: They instinctively recognize which emotions an other animal is expressing with its voice. Now scientists have verified if this is correct. Therefor they let 75 subjects listen to sound recordings of pigs, apes, elephants, pandas, frogs, alligators, crows and tomtits.

The sounds were taken from animals in a relaxed, neutral mood or an excited mood like fear and anger. The human subjects had to state the grade of excitement when listening to the sounds.

High hit ratio

The result: The subjects correctly estimated the emotional content of almost every sound, independent of how tight the species was related to us. In the case of a panda and treefrog the subjects were correct in about 90 percent. In case of alligators, elephants and tomtits about 80 percent were correct. The sound of crows, pigs and apes reached more than 60 percent regarding correctness.

Thereby hit ratio of all species was significantly higher than random.

Filippi and colleagues state. Further analysis shows, that emotions in the sound are characterized by two features: a higher ground tone of sound and the position of the middle point of sound spectrum.

A universal code?

This proves, that humans are able to recognize upset mood in the sounds of tetrapods of all species.

Because the subjects were from the German, English and Chinese language regions, scientists think this could be a basic human ability.

Therefore Darwin could have been correct with his hypotheses. According to Filippi and his colleagues their result shows, that there is actually a kind of universal code for vocal expression of emotions in the animal world. The ability to decode this emotional code, reaches far back to our evolutionary past.

Source: Proceedings of the Royal Society B – Biological Sciences, 2017; doi: 10.1098/rspb.2017.0990