Dog brains represent the meaning of action words

One does not need to be a dog owner to wonder about

why dogs sit upon hearing the command “Sit!”.

Do they know what to do from the context? Or do they automatically initiate the movement when recognizing the sound sequence associated with it? Or maybe dogs, like humans, actually understand that the given word refers to the action itself?

“Word processing unfolds as a multi-stage process in the human brain,” explains Marianna Boros, a researcher in the Neuroethology of Communication Lab at the ELTE University’s Department of Ethology and one of the study’s authors. “Understanding a word involves more than simply recognizing its sound form: the brain must also access the meaning associated with that word. In humans, word meanings are grounded in mental representations of the referents, we have an internal ‘image’, a kind of mental equivalent, of the thing the word refers to. Importantly, while sound patterns are primarily processed in the auditory cortex, word meaning can also engage brain regions related to the represented concept itself. For example, action words can activate brain areas involved in motor control. This is one of the key principles we took advantage of in the present experiment.” 

To find out whether the brains of family dogs, who live in the linguistic environment of humans, process words similarly to the human brain, the researchers invited MR-trained family dogs to participate in an fMRI experiment. As illustrated in a short video abstract about the study, the dogs were presented with familiar action instruction words and meaningless nonwords while lying motionless in an MRI scanner. The researchers found that instruction words triggered stronger brain activity than nonwords not only in auditory but also in movement control regions. This revealed that dogs can not only recognize sound sequences that constitute words, but also process their meanings. Most importantly, words with similar meanings, like ‘come’ and ‘go’, both involving locomotion, were processed more similarly to each other than to words like ‘stay’ and ‘lie,’ which don’t involve moving around. This meaning-based categorization closely resembles the way the human brain stores word meanings by forming a so-called semantic network. 

“It is particularly exciting that during the experiment the dogs were not allowed to carry out the spoken instructions, there was no relevant behavioral context, yet we observed activation in motor-related brain areas in response to the words,” emphasizes Dorottya Rácz, PhD student at the lab, also an author of the study. “All this reinforces the idea that dogs’ word processing does not consist merely of simple associations, but that, similarly to humans, they may be able to link words to the mental representation of their referents. Put simply, upon hearing a word, a mental image of what the word means may appear in the dog’s brain. One explanation for these similarities in dogs’ and humans’ semantic capacities may be that living in a language-rich environment, dogs’ brains may have started to adapt to processing this evolutionarily novel, yet highly relevant stimulus: speech.” 

The researchers also compared the dogs’ brain responses to real instruction words to slightly altered versions, where only a single sound was changed. “For humans, in most of the cases every sound in a word matters, because changing even one sound can result in an entirely different word. Accordingly, by around two years of age, children show different responses to real, meaningful words than to phonetically similar, but nonsense sound sequences” adds Attila Andics, head of the research lab and also an author of this work. The dog brain, however, unlike the human brain, didn’t seem to notice the difference. “This finding indicates that dogs may not store the sounds of words as precisely as we do. Perhaps because they do not even need to, given that they know far fewer words.” 

This research is the first to show that although dogs do not pay as much attention to the phonetic details of words, they still store word meanings in surprisingly human-like ways. 

This study was published in NeuroImage titled “Action instruction word processing in the dog brain entails both auditory form identification and meaning representation”, written by Marianna Boros, Dorottya S. Rácz, Attila Andics.

The study was funded by:

Eötvös Loránd University; Ministry for Culture and Innovation from the source of the National Research, Development and Innovation Fund; European Research Council; National Brain Research Program