While people have long believed their dogs understand what they're saying, a new study suggests they are processing the meaning and emotion of words in a human-like way.
Past research has shown that dogs respond to different parts of human speech -- including the actual content and the emotional tone, said study author Victoria Ratcliffe.
But her team's findings give a deeper insight into the canine brain, according to Ratcliffe, a Ph.D. candidate at the University of Sussex in the United Kingdom.
For one, the study found, dogs seem to process multiple components of human speech all at once. What's more, their brains are human-like in the way they distinguish the information in words from the emotional tone.
That does not mean dogs are actually understanding all the words people say, Ratcliffe stressed.
But, she said, the findings do suggest that "dogs may dissociate and process speech components in a way that is broadly comparable to humans."
Ratcliffe and colleague David Reby report their findings in the Nov. 26 issue of Current Biology.
The results probably won't shock dog owners, noted Nicholas Dodman, a professor of animal behavior at the Tufts University Cummings School of Veterinary Medicine in North Grafton, Mass.
"No, dogs are not going to read books or compose sonnets," said Dodman, who was not involved in the study. "But they can take quite a bit out of what we're saying. They are picking up certain sounds that have meaning for them. They're also picking up the tenor of what we're saying," he explained.
"I'd say it's a testament to their abilities as sentient beings," Dodman added.
For the study, Ratcliffe and Reby had dogs listen to human speech from two speakers placed on either side of the animal. The speech either had meaning to the dog (the very British command, "Come on then") or no meaning.
The quality of the speech was also manipulated: Sometimes it was stripped of the trappings of the human voice, to emphasize the meaning of the words; sometimes the emotional tone was exaggerated.
The researchers found that when they broadcast "come on then" with the meaning emphasized, the dogs typically turned their heads to the right-side speaker. That, according to Ratcliffe, indicates they were processing the words with a bias toward the left hemisphere of the brain -- which in humans is the half that picks up the sound and syntax of words.
On the other hand, when the emotional tone of the speech was exaggerated, the dogs turned to the left -- which indicates that the brain's right hemisphere was dominant. And in humans, the right hemisphere processes the intonation and emotional quality of speech.
"To me," Dodman said, "this is another step in our realization that dogs are more attuned to us than we've previously recognized."
That's important for a few reasons, according to Ratcliffe. "Developing our understanding of how dogs perceive human speech is obviously beneficial in improving our communication with them," she said.
But there are also implications for understanding humans and other mammals. "In evolutionary terms," Ratcliffe said, "we can directly compare humans and dogs to see which attributes of speech perception are uniquely human, or part of a shared mammalian history that encompasses dogs as well."
For people who live with dogs, the findings probably just validate what they've already "intuitively known," according to Dodman. But he said scientific studies of canine behavior are important.
And as these findings suggest, he said, "dogs have been studying us for a long time."