Dogs can’t tell the difference between words that differ by only one sound, according to new research published on December 9 in the journal Royal Society Open Science.
Scientists have long studied the relationship between humans and dogs, and the new research highlights a specific skill and shortcoming of our canine companions. While the dogs in the study could recognize the commands they’d been taught, they also responded to nonsense versions of the same word that had one of the vowel sounds altered. Words like “sit” and a nonsense alternative, “sut,” might sound the same. The researchers measured the dogs’ brain activity with electroencephalography—electrodes taped to the dog’s head to measure the electrical equivalent of a dog perking up when it hears something it recognizes. For comparison, the researchers also said nonsense words that sounded nothing like the command.
"The brain activity is different when they listen to the instructions, which they know, and to the very different nonsense words, which means that dogs recognize these words," says animal behavior researcher Lilla Magyari to CNN’s Amy Woodyatt.
Magyari led the research at Eötvös Loránd University in Budapest, Hungary, and the tests were conducted in Hungarian. So to test the dogs’ reaction to the command “Fekszik,” which means “lay down,” they compared it with a similar but nonsensical word, “Fakszik,” Magyari tells Ari Shapiro and Ailsa Chang at NPR. They also measured the dogs’ response to a total nonsense word, “Matszer.” The only thing it has in common with fekszik is the fact that it has the same sequence of consonant and vowel sounds.
The researchers found that the dogs’ electrical activity lit up for both “Fekszik” and “Fakszik,” but not for “Matszer,” which means the dogs recognize the significance of the command but can’t tell the two similar words apart even though the words sound different to humans.
"They may just not realize that all details, the speech sounds, are really important in human speech,” Magyari tells CNN. “If you think of a normal dog: That dog is able to learn only a few instructions in its life.”
The scientists worked with family dogs that hadn’t been specifically trained for the experiment. Instead, the researchers tried to create a relaxing environment for the dogs. A few of the pups were so excited to participate in the study that they had to drop out because the electrodes wouldn’t stay on their heads. The researchers note in their paper that the drop-out rate was about equal to the rate in human infant studies.
Recognizing words without caring about the details is a similar level of language understanding to infants of about 14 months old, according to a statement released by Eötvös Loránd University. The difference is that while infants pick up an incredible library of phonetic sounds between 14 and 20 months, dogs never progress any further.
“We sort of evolved with dogs to be sort of socially attuned to one another,” says Amritha Mallikarjun, who studies dogs at the Penn Vet Working Dog Center, to NPR. Ever since “the first wolf that came over and wanted snacks from the early human…we've been sort of reading each other's social cues really, really well.
“And part of human social behavior is language. So it's important for dogs to sort of pay attention to our linguistic cues as one way of better understanding us.”
Mallikarjun had previously led studies that also found that dogs have a hard time telling words apart if they rhyme. So if you have two dogs, she recommends giving them very different names so that they don’t get confused, for example.
Although the research all suggests limits on dogs’ language skills, it also has the upside of proving that the dogs do listen to words, and don’t just respond to general tone and body language. So rest assured that whether your dogs have learned hundreds of words or just a dozen, they’re all very good pups.