Dogs just don’t listen.

Or maybe more to the point, dogs can’t listen. Not the way humans can, anyway. Despite dogs’ excellent hearing and similarities in the way both species process words, dogs don’t hear the subtle differences between words the way that humans do, according to a new study from researchers at Eötvös Loránd University in Budapest, Hungary.

The researchers had theorized that this might be a reason why, despite living with people and hearing them speak their whole lives, the number of actual words dogs learn to recognize generally remains very low.

To test their theory, the researchers measured the brain activity of family dogs using electroencephalography (EEG), which is noninvasive but did involve taping electrodes to the dogs’ heads.

The researchers played a series of recorded words for the dogs. The words consisted of real instruction words the dogs knew—such as “sit”—and similar-sounding but nonsensical words that differed by only one letter, such as “sut,” followed by very different-sounding nonsensical words such as “bep.”

Corresponding author Lilla Magyari, a postdoctoral researcher at Eötvös Loránd University, told NEWStat that “It’s puzzling that most dogs can learn only a few words throughout their lives despite their excellent auditory capacities and social skills.” She said she and her colleagues hoped that the study would shed some light on the reasons for that.

“The analysis of the recorded brain activity showed that dog brains clearly and quickly distinguished the known instruction words from the very different nonsense words,” such as bep. But she said the EEG showed they had trouble distinguishing between the instruction words they knew and nonsense words that differed in a single speech sound—such as between “sit” and “sut.”

Magyari said that EEG is a very good way to measure brain activity on a millisecond timescale, and their results show that the dogs’ brains quickly discriminated the known words from the nonsense words as quickly as 200 milliseconds after the beginning of the words. “This effect is in line with similar studies on humans that show that the human brain responds differently to meaningful and nonsense words within a few hundred milliseconds.”

Magyari and her colleagues speculate that the similarity of dogs’ brain activity for instruction words they know and for similar nonsense words reflects not perceptual constraints, but attentional and processing biases: “Dogs might not attend to all details of speech sound when they listen to words. Further research could reveal whether this could be a reason that incapacitates dogs from acquiring a sizable vocabulary.”

Regardless, Magyari says dogs definitely listen to people when they talk, but that doesn’t mean you need to start watching what you say: “They might recognize a few words,” she said, “[But] many dogs probably don’t understand a lot.”

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