Dog brains can detect speech and show different activity patterns to familiar and unfamiliar languages, according to a new brain-imaging study published in NeuroImage (“Speech Naturalness Detection and Language Representation in the Dog Brain”) by researchers from the Department of Ethology at Eötvös Loránd University, Hungary. This is the first demonstration that a nonhuman brain can differentiate two languages.
“Some years ago, I moved from Mexico to Hungary to join the Neuroethology of Communication Lab at the Department of Ethology, Eötvös Loránd University, for my postdoctoral research,” says Laura V. Cuaya, first author of the study. “My dog, Kun-Kun, came with me.
“Before, I had only talked to him in Spanish. So I was wondering whether Kun-Kun noticed that people in Budapest spoke a different language, Hungarian. We know that people, even preverbal human infants, notice the difference. But maybe dogs do not bother. After all, we never draw our dogs’ attention to how a specific language sounds. We designed a brain-imaging study to find this out.
“Kun-Kun and 17 other dogs were trained to lie motionless in a brain scanner, where we played them speech excerpts from The Little Prince in Spanish and Hungarian. All the dogs had heard only one of the two languages from their owners, so this way, we could compare a highly familiar language to a completely unfamiliar one.
We also played the dogs scrambled versions of these excerpts, which sound completely unnatural, to test whether they detect the difference between speech and nonspeech at all.”
When comparing brain responses to speech and nonspeech, the researchers found distinct activity patterns in the dogs’ primary auditory cortexes. This distinction was there independently of whether the stimuli originated from the familiar or the unfamiliar language. There was, however, no evidence that dog brains would have a neural preference for speech over nonspeech.
“Dog brains, like human brains, can distinguish between speech and nonspeech. But the mechanism underlying this speech detection ability may be different from speech sensitivity in humans: whereas human brains are specially tuned to speech, dog brains may simply detect the naturalness of the sound,” explains Raúl Hernández-Pérez, coauthor of the study.
In addition to speech detection, dog brains could also distinguish between Spanish and Hungarian.
These language-specific activity patterns were found in another brain region, the secondary auditory cortex. Interestingly, the older the dog was, the better their brain distinguished between the familiar and the unfamiliar language. “Each language is characterized by a variety of auditory regularities. Our findings suggest that during their lives with humans, dogs pick up on the auditory regularities of the language they are exposed to,” says Hernández-Pérez.
“This study showed for the first time that a nonhuman brain can distinguish between two languages,” says Attila Andics, senior author of the study. “It is exciting, because it reveals that the capacity to learn about the regularities of a language is not uniquely human. Still, we do not know whether this capacity is dogs’ specialty or general among nonhuman species.
“Indeed, it is possible that the brain changes from the tens of thousands of years that dogs have been living with humans have made them better language listeners, but this is not necessarily the case. Future studies will have to find this out.”
