In the first demonstration that a non-human brain can differentiate two languages, researchers at Etvs Lornd University in Hungary have shown dog brains can detect speech.
The brain imaging study - published in Neurolmage - shows dog brains display different activity patterns in response to a familiar and unfamiliar language.
They also found dogs can distinguish between speech and non-speech - so if you speak gibberish to your pup, they might even know that you're talking nonsense.
The research was sparked when Dr Laura V. Cuaya, lead author of the study, moved from Mexico to Hungary, bringing her dog Kun-kun with her.
"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," Dr Cuaya said.
"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."
Kun-kun and 17 other dogs were trained to lay very still within a brain scanner. Using functional magnetic resonance imaging (fMRI), brain activity could be measured by detecting changes associated with blood flow; when an area of the brain is being used, the blood flow to that area increases.
They were played excerpts of the Antoine de Saint-Exupéry classic, The Little Prince, in Spanish and Hungarian.
All dogs had either heard one or the other language from their owners during their lives, so the researchers could compare their reaction to a highly familiar language from a completely unfamiliar one.
Going a step further the researchers played the pups scrambled versions of these excerpts - which sound completely irregular - to see whether they could distinguish between real speech and non-speech as well.
Of course, they could.
When comparing the brain responses to speech and non-speech, there were distinct activity patterns in the dogs' primary auditory cortex. These patterns were independent from whether the real speech stimuli originated from the familiar or unfamiliar language.
But according to co-author Dr Ral Hernndez-Pérez, while dog brains can differentiate between speech and non-speech, that doesn't mean they understand what we say.
"Dog brains, like human brains, can distinguish between speech and non-speech," Dr Hernndez-Pérez said.
"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."
Dogs also showed language-specific activity patterns found in another brain region - the secondary auditory cortex, and it also seems possible the cliché about old dogs will need an update: the older the dog was, the better they could distinguish between the language that was familiar and unfamiliar to them.
"Each language is characterised 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," Dr Hernndez-Pérez said.
This is the first time a non-human brain has been shown to be able to distinguish between two languages, and means the capacity to learn about the regularities of language is not as uniquely human as we may have thought.
However, according to senior author Dr Attila Andics we still don't know whether this capacity is general among all non-human species, or is just a canine specialty.
"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," Dr Andics said.
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