Consonants and vowels play different roles in speech perception: Humans rely more heavily on information gleaned from hearing consonants than on information gleaned from vowels when distinguishing between words.

Dogs are different.

They pay attention to the vowels. That’s among the findings of a new study by researchers at the University of Maryland published last month in Animal Cognition.

For the study, the researchers recruited 44 dogs and played them prerecorded, deliberately mispronounced versions of their names—one version featuring the wrong vowels, the other featuring the wrong consonants—as well as correctly pronounced versions.

They found that dogs tend to pay more attention to vowels than to consonants when they’re trying to suss out what humans are saying to them. Linguists call this a bias for vowels. And it’s pretty much the exact opposite of the way humans process language when trying to understand each other: Humans have a bias for consonants.

“Dogs demonstrated a vowel bias rather than a consonant bias, preferring their own name over a vowel-mispronounced version of their name,” the researchers wrote, “but not in comparison to a consonant-mispronounced version.”

In other words, dogs preferred their own correctly pronounced name to a version with a mispronounced vowel (think Spot versus Spit). But it didn’t seem to have much of an impact on their understanding if the consonants in their name were wrong (Spot versus Spod).

NEWStat talked to lead author Amritha Mallikarjun, MS, PhD, a postdoctoral researcher in Neuroscience and Cognitive Science at the Penn Vet Working Dog Center, to find out more.

NEWStat: It seems that your research is primarily concerned with the development of speech in infants; why did you use dogs in this study?

Amritha Mallikarjun: We used dogs in this study for a few important reasons. First, pet dogs get natural, long-term language exposure from their owners. Second, dogs are “interested” in the language spoken to them. Dogs are very socially attuned to human behavior and speech, and easily pick up on meanings of word forms and gestures. As such, dogs are a great model species to compare to infants; dogs can show us how much linguistic structure can develop from natural language exposure and social cognition alone, without the human linguistic system.

NEWStat: How do dogs learn to distinguish human speech, and what role do vowels play versus consonants?

AM: Dogs hear speech naturally in their environment, both from people speaking directly to the dog and from the dog overhearing conversations. As such, they are able to learn several words and their meanings. When scientists examined the role of consonants and vowels in human language, they found that, in general, consonants are what people use to determine word identity, and vowels help determine other features, like tone and prosody (the rhythm, stress, and intonation of speech, which provide important information beyond a sentence’s literal meaning). We wanted to see whether dogs naturally used consonants to help figure out word identity, the way that adult humans and older infants do. We found that dogs are actually more attuned to the vowels in words and will notice when you change a vowel in a familiar word, but not when you change a consonant.

NEWStat: How can your findings help veterinary professionals practice better medicine?

AM: This research can help veterinarians guide their clients to select optimal names for their pets. For example, if you [already] have a dog named Ella, you don’t want to name your new puppy Stella, as your dogs will have difficulty telling these words apart. Additionally, commands for dogs should [have different vowels]. For example, “stay” and “lay” are not ideal commands because they only differ in consonants.

Other research done by our lab has more practical applications for veterinarians. A 2019 study, “The cocktail party effect in the domestic dog” looked at dogs’ ability to understand their own names in the presence of background noise. Dogs struggled at a level that is relatively easy for adult humans. [Animal hospitals] can be noisy places, so it’s important to consider that when you talk to a dog or give commands to a dog in that kind of environment—they may struggle to understand you. As such, it might be worthwhile to always give concurrent visual commands in noisy environments to help the dog better understand what you’re asking of them.

NEWStat: What do you hope will be the chief takeaways from your study?

AM: [Our findings] are especially important for dogs who have many commands in their repertoire—service dogs, search-and-rescue dogs, and dogs who participate in obedience or other dog sports. When selecting commands, it can be hard to avoid words that share a similar vowel, such as “down” and “bow.” Ideally, commands won’t share vowels, or will also differ in other features, such as the number of syllables. For example, you can change “bow” to “take a bow.”

There’s not a lot of current research examining dogs’ auditory processing and attention (though this fascinating study is in the works). We hope that our studies also spark more interest and collaboration with the veterinary community to further study how dogs process sounds and speech in their environments and how it affects their lives.

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