Thousands of years of domestication have left dogs with a remarkable capacity to comprehend human speech, and new research reveals that the brains of our four-legged friends are even able to differentiate between languages. Appearing in the journal NeuroImage, the new study is the first to detect such an ability in any non-human animal.
To conduct their research, the study authors trained 18 pet dogs to lie motionless inside a functional magnetic resonance imaging (fMRI) scanner so that their brain activity could be recorded while they listened to audio recordings of human speech. Two of the dogs involved in the study came from homes that spoke exclusively Spanish, while the remaining 16 belonged to Hungarian-speaking families.
While in the scanner, each dog listened to an excerpt from Antoine de Saint-Exupéry’s The Little Prince in both Spanish and Hungarian. They also heard scrambled versions of these recordings that made no sense and sounded completely unnatural.
When analyzing the responses of the dogs’ brains to these recordings, the researchers noted that activity patterns within the animals’ primary auditory cortex differed depending on whether they heard actual speech or scrambled nonsense. This suggests that dogs are indeed able to tell the difference between speech and non-speech, regardless of the language spoken.
According to study author Raúl Hernández-Pérez, this observation is most likely to reflect dogs’ ability to “detect the naturalness of the sound" rather than a capacity to identify human speech per se.
Building on this finding, the researchers then compared activity patterns within the dogs’ brains when they listened to recordings in their familiar language versus a foreign language. Interestingly, these language-specific patterns were located within a different region, known as the secondary auditory cortex, indicating that “separate cortical regions support speech naturalness detection and language representation in the dog brain.”
The researchers also found that this neural response to language was more pronounced in older dogs, leading them to conclude that longer exposure to human speech enables pet pooches to refine their linguistic recognition skills. In addition, these activity patterns were stronger in longer-headed dogs, hinting at differences between breeds when it comes to processing human speech.
In a statement, study author Attila Andics explained these findings indicate that “the capacity to learn about the regularities of a language is not uniquely human.” However, it remains to be seen “whether this capacity is dogs’ specialty, or general among non-human 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.”