(ORDO NEWS) — The dogs, who were given to listen to excerpts from “The Little Prince” in Hungarian and Spanish, demonstrated the ability not only to recognize the “native” language, but also to distinguish natural speech from “encrypted”.
Scientists from the Eotvos Laurent University in Budapest (Hungary) conducted a small experiment, as a result of which they were able to confirm that dogs are able to distinguish natural human speech from an arbitrary set of sounds and recognize the language spoken by their owners. The research results are published in the journal NeuroImage.
The authors of the work note that each language has acoustic patterns, such as prosodic features (for example, pronunciation, pitch, and so on) or the distribution of sounds in speech, which a person learns long before he fully masters the language.
So, in infancy, we are already able to distinguish speech from non-speech stimuli: birdsong, sneezing, mosquito squeak, and so on.
“Infants also distinguish between familiar and unfamiliar languages belonging to different rhythmic classes. Meanwhile, to distinguish between two languages of the same rhythmic class requires preliminary acquaintance with one of the two, “the scientists write.
Previous studies have shown that macaques can also distinguish natural speech from “scrambled” (speech signal in which parts of the spectrum are inverted and shifted in frequency).
However, neither babies, nor monkeys, nor rats, nor birds in the experiments were able to distinguish speech stimuli of different languages if they were reproduced in the reverse order. Therefore, this ability is based on properties unique to speech, and not simply on distinguishing complex acoustic stimuli in general.
Dogs have long lived next to humans: according to some reports , they were domesticated 23 thousand years ago.
The voice in general and our speech in particular are not only familiar to dogs, but also extremely important for them: these animals are sensitive to both segmental (linear: sounds, syllables, phonetic word, etc.) and supersegmental (nonlinear: stress and intonation ) sound units.
From these signals, dogs can identify the speaker, recognize their emotional state, and distinguish between the words themselves. Some behavioral studies have shown that some breeds have an exceptionally large vocabulary and quickly learn the names of new subjects.
But, despite the many scientific works, until now scientists have not received evidence that dogs are able to distinguish between natural speech and non-speech stimuli. In addition, although pets get used to a certain human language and are “surrounded” by it, it was not clear whether they were able to isolate its patterns and distinguish it from the unfamiliar.
The aim of the new study was to test whether dogs respond specifically to speech and whether they are able to learn “native” language. The scientists also wanted to identify the neural processes involved in this.
The experiment involved 18 animals of different breeds: nine bitches aged from three to 11 years, five golden retrievers, six border collies, two Australian shepherds, one labradoodle, cocker spaniel and three mixed breeds.
The dogs, on which they put on headphones (they were not given any sedatives), underwent MRI scans, while listening to the chapter of the famous fairy tale “The Little Prince” by the French writer Antoine de Saint-Exupery. The text was read by two unfamiliar women – in Hungarian and Spanish. In some cases, audio recordings were divided into smaller parts and assembled in a different order.
“Hungarian was a language that was spoken among 16 dogs, Spanish was“ familiar ”to two dogs. Although Hungarian and Spanish differ in both segment units and super segment units, both belong to the same rhythmic class, ”the researchers noted.
As shown by the results of MRI, the brains of dogs showed different patterns of activity in the primary auditory cortex for natural versus “scrambled” speech.
“We’ve identified specific areas in the dog’s brain that code for functions that make it possible to recognize speech or identify language. We also identified patterns of activity for natural speech versus encrypted speech, ”the scientists write.
The sounds of familiar and unfamiliar languages evoked different reactions in the secondary (or associative) auditory cortex and cruciate groove, but only when the animals were listening to natural speech. The difference was especially noticed by older dogs.
According to the researchers, this reflects a sensitivity to linguistic patterns, and not to the voice signals themselves and the characteristics of the person speaking. By the way, the more elongated the dog’s skull was, the better it distinguished natural speech from “scrambled” speech.
“Our study has shown for the first time that a non-human brain can distinguish between two languages,” the scientists concluded.
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