In some good news for dog-owners who spend considerable time talking to their pets, researchers have found that the canines pay attention to what we say and how we say it.
The study provides some of the first evidence of how dogs differentiate and process various components of human speech.
"Although we cannot say how much or in what way dogs understand information in speech from our study, we can say that dogs react to both verbal and speaker-related information and that these components appear to be processed in different areas of the dog's brain," said Victoria Ratcliffe of the School of Psychology at the University of Sussex.
Previous studies showed that dogs have hemispheric biases - left brain versus right - when they process the vocalisation sounds of other dogs.
Ratcliffe and her supervisor David Reby investigated whether dogs show similar biases in response to the information transmitted in human speech.
They played speech from either side of the dog so that the sounds entered each of their ears at the same time and with the same amplitude.
"The input from each ear is mainly transmitted to the opposite hemisphere of the brain," Ratcliffe said.
"If one hemisphere is more specialised in processing certain information in the sound, then that information is perceived as coming from the opposite ear," said Ratcliffe.
If the dog turned to its left, that showed the information in the sound being played was heard more prominently by the left ear, suggesting that the right hemisphere is more specialised in processing that kind of information.
The researchers did observe general biases in dogs' responses to particular aspects of human speech.
When presented with familiar spoken commands in which the meaningful components of words were made more obvious, dogs showed a left-hemisphere processing bias, as indicated by turning to the right.
When the intonation or speaker-related vocal cues were exaggerated instead, dogs showed a significant right-hemisphere bias.
"This is particularly interesting because our results suggest that the processing of speech components in the dog's brain is divided between the two hemispheres in a way that is actually very similar to the way it is separated in the human brain," Reby said.
It does not mean that dogs actually understand everything that we humans might say or that they have a human-like ability of language, researchers said.But Ratcliffe said these results support the idea that our canine companions are paying attention "not only to who we are and how we say things, but also to what we say."
The research was published in the Cell Press journal Current Biology
