Dogs are not only able to understand what people are saying, but also the way they are saying them, researchers have discovered.
Experts from the University of Sussex have found the first evidence to suggest dogs are able to process components of human speech including emotional tone and gender.
Published in the Cell Press journal Current Biology, Victoria Ratcliffe said their findings indicate dogs may not understand every word that is being said but they are trying.
Ratcliffe said: "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."
Researchers were looking at previous research that showed dogs have hemispheric brains (left and right) when they process sounds made by other dogs. The team was looking to find out if this was the same when responding to human speech.
They played a group of dogs' recordings of speech in surround sound and looked to see if the dog turned right or left.
"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."
In total, 280 dogs were tested. Of these, 250 responded and 30 did not.
When the dogs were played sounds where all of the verbal information was taken out, for example someone making a humming sound but varying the pitch or speaking a foreign language, the dogs turned left suggesting the right hemisphere of the brain was being used.
This shows the dog is working out non-verbal information about the speaker. In humans, this would amount to gender and identity, etc.
When played verbal recordings, the dogs used the left hemisphere of their brains to process the information.
The findings suggest dogs are able to separate out the information they are being provided and are paying attention to more than one aspect of speech at the same time.
Ratcliffe told IBTimes UK: "They are paying attention to what you're saying to them. They are getting more from us than we previously thought."
One of the potential theories about why dogs can do that is its evolutionary purpose.
"It could be that we've selected dogs that are better at responding to speech and human vocal commands because they're the dogs that are going to be the best ones if you want to use them for cooperating with people," she said.
"It could be we selected dogs that are most likely to have similar ways of processing information of speech to us. That would be conversion evolution.
"Any way they can get information out is going to be beneficial to them in how they interact with people, the fact they can get more out than we thought before would be an advantage to them.
"Obviously most dogs live with people - more than they interact with other members of their own species - so it's really important they communicate with us and to be able to know what we're trying to communicate to them."
However, Ratcliffe also said it could be that other animals process speech in this way – and this is what they plan to test next.
She said: "We'd like to compare other domesticated animals and animals that are not domesticated but have been exposed to speech. We'd also like to look at the function of the information, so we know how they are dividing it to get the information out and what's important – do they use it in the same way we do?"