Dogs’ brain activity shows they recognize the names of objects

Needle, a cheerful miniature schnauzer I had as a kid, turned into a ball of unspeakable noise and fury each time she saw a dog called Puma. She hated Puma so much she would go ballistic, barking and growling. Merely whispering the name “Puma” set off the same reaction, as though the sound of it and the idea of the dog it represented were clearly connected deep in Needle’s mind.

A connection between a word and a mental representation of its meaning is called “referential understanding,” and for a very long time, we believed dogs lacked this ability. Now, a study published by a team of Hungarian researchers indicates we might have been wrong.

Practice makes perfect

The idea that dogs couldn’t form associations with language in a referential manner grew out of behavioral studies in which dogs were asked to do a selective fetching task. The canines had a few objects placed in front of them (like a toy or a bone) and then had to fetch the one specifically named by their owner.

“In laboratory conditions, the dogs performed at random, fetching whatever they could grab first, even though their owners claimed they knew the names of the objects," said Marianna Boros, a researcher at Neuroethology of Communication Lab at Eötvös Loránd University in Budapest, Hungary. "But the problem is when the dogs are not trained for the task, there are hundreds of things that can disturb them. They can be more interested in one specific toy, they may be bored, or they may not understand the task. So many distractions.”

To get around the issue of distractions, her team checked to see if the dogs could understand words passively using EEG brain monitoring. In humans, the EEG reading that is considered a telltale sign of semantic reasoning is the N400 effect.

“The work on the N400 was first published in 1981, and hundreds of studies replicated it since then with different stimuli. Typically, you show images of objects to the subject and say matching or mismatching names. When you measure EEG brain activity, you will see it looks different in match and mismatch scenarios,” explained Lilla Magyari, also a scientist at Neuroethology of Communication Lab and co-author of the study. (It’s called the N400 effect because the peak of this difference appears around 400 milliseconds after an object is presented, Magyari explained.)

The only change the team made to adapt a standard N400 test to dogs was switching the order of stimuli—the words were uttered first, and the matching or mismatching objects were shown second. “Because when they hear the word which activates mental representation of the object, they are expecting to see it. The sound made them more attentive,” said Magyari.

Timing is everything

In the experiment, the dogs started out lying on a mat with EEG gear on their heads in a room with an experimenter or the owner of a different dog. The owner of the dog being tested was separated by a glass pane with controllable opaqueness. “It was important because EEG studies [can] very precisely time the moment of presentation of your stimulus,” said Boros.

Sentences spoken by the owners that would get the dogs’ attention—things like “Kun-kun, look! The ball!”—were recorded and played to each dog through a loudspeaker. Then, 2,000 milliseconds after each dog heard the sentence, the pane would turn transparent, and the owner would appear holding a matching or mismatching toy. “Each test lasted for as long as the dog was happy to participate. The moment it started to get up or look away, we just stopped the test, and the dog could leave the mat and we just finished by playing sessions. It was all super dog-friendly,” Boros said.

For most dogs in the study, an EEG reading similar to the human N400 appeared between 200 and 600 milliseconds after they saw the object. The mismatch effect was stronger the more they were familiar with the item they saw—a favorite toy that was mentioned but didn’t appear caused a stronger reaction, as measured by the EEG. “It was not only about the association of words with objects. Like, often when I see a ball I also hear the word ‘ball,’ so I know they somehow belong together. Introducing this little bit of delay in presentation led us to think dogs actually had expectations to see the object based on their mental representations,” said Magyari.

In previous referential understanding studies with parrots, bottleneck dolphins, apes, and even some dogs, the animals were always specifically trained to perform in the tests. “We did a study on untrained, very typical dogs,” said Boros. This was to determine whether semantics might only be a feature found in a few exceptional individuals. For the first time, there is strong evidence that it’s a capacity all dogs have as a species. But if so, dogs should have been able to breeze through all those selective fetching tests. So why didn’t they?

You are what you eat

“When you think about their evolution, ever since dogs were domesticated 18,000 to 30,000 years ago, they were selected for specific, action-oriented functions like herding, hunting, etc. These functions were not really connected with objects,” said Boros.

Dogs understand action words like "sit," "come," or "fetch" much better than object words because that’s what they’ve always heard from us. “But today, family dogs are living in a completely different environment than they did through most of their evolutionary history,” Boros added. Modern dogs mostly live with us in our homes, and human homes are full of stuff and full of language. What we see might just be evolution catching up to this. But there is another reason.

“Puma” was among a very small list of words that triggered such an enormous emotional response in my Needle. One of those words referred to the dog she hated, and others referred to the people she loved—to me and my family. None were objects like the ones used in these tests.

“Dogs are very social. They are not really interested in objects. But they are super-interested in humans, especially their owners,” said Boros. It may be that in those selective fetching studies, dogs could tell one bouncy, shiny, plasticky gadget from the other. It just didn’t matter to them when there was a human there to interact with. “Communicating with your dog, you need to keep in mind it understands more than it shows,” said Magyari.

Current Biology, 2024.  DOI: 10.1016/j.cub.2024.02.029.