“This is not your food! Don’t even think about eating it. This … is … not … your … food.” What do our words mean to dogs? Not that I’m about to stop speaking to dogs anytime soon, but I do wonder what my daily utterances signify to Millie, Piper, Upton and Finnegan, the dogs I converse with on a regular basis. Do I sound like a cross between Charlie Brown’s teacher and Gary Larson’s “What Dogs Hear” cartoon? Are we on the same page, or even in the same book?

I set out on a quest to explore dogs and their understanding of human language. What do we think dogs understand? A lot, according to a study by Péter Pongrácz and his colleagues at the Family Dog Project in Budapest. Thirty-seven owners provided a list of 430 different utterances that they thought their dogs knew, with each owner providing an average of 30 phrases.

Enter Rico, Chaser, Sofia, Bailey, Paddy and Betsy, companion dogs celebrated for their panache for human language. The news media hails them as “super smart,” and after meeting Chaser, astrophysicist Neil deGrasse Tyson exclaimed, “Who would have thought that animals are capable of this much display of intellect?”

So what are these dogs doing with words?

Objects
Dogs can learn the names of many, many, many different objects. Julia Fischer, group leader at the German Primate Center’s Cognitive Ethology Lab, heard that a Border Collie named Rico knew the names of 70 individual objects, and she wanted to know how Rico mapped specific human words to particular objects. “I contacted the owners, and they let us visit their home and start a study of Rico,” explains Fischer. This culminated in 2004 with an article in Science, reporting that Rico knew the names of over 200 different objects.

Seven years later, Chaser, a Border Collie in South Carolina, took the gold medal when Alliston Reid and John Pilley of Wofford College reported that Chaser knew the distinct names of 1,022 objects — more than 800 cloth animals, 116 balls, 26 Frisbees and 100 plastic items. Chaser knows that “Uncle Fuzz” is different from “Wise Owl,” who is certainly different from “Merlin.” This is not merely a story about Border Collies, however. Researchers recently related that Bailey, a 12-year-old Yorkshire Terrier, knows the names of about 120 toys.

Chaser and Rico also win praise for their ability to learn and retain the names of new objects. When presented with a group of toys, all of which were familiar except one, the dogs could retrieve the unknown toy when asked to fetch using an unfamiliar word. In essence, the dogs were pairing a novel object with an unfamiliar name after a single association and then remembering the name of that new object in subsequent trials. In children, this is called “fast mapping,” and it was thought to be uniquely human. Pilley notes, “This research shows that this understanding occurs on a single trial. However, Chaser needed addition rehearsal in order to transfer this understanding or learning into long-term memory.”

Actions
But life is not only about knowing the names of one’s stuffies and Frisbees. Humans often use verbs such as come, sit, down and off to get dogs to alter their behavior. After controlling for outside contextual cues, researchers found that dogs could still understand that specific words map to specific physical actions. Chaser showed an incredible amount of flexibility with actions — performing “take,” “paw” and “nose” toward different objects.

“That’s just training,” you might say, but this suggests that some dogs show a cognitively advanced skill where actions are understood as independent from objects. Reid and Pilley found that Chaser does not interpret “fetch sock” as one single word, like “fetchsock.” Instead, she can perform a number of different actions flexibly toward a number of different objects. Daniela Ramos, a veterinary behaviorist in São Paulo, discovered that a mutt named Sofia could also differentiate object names from action commands, suggesting these dogs attend to the individual meaning of each word.