Puppy dog eyes are for the benefit of humans, scientists find

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When researchers at the University of Portsmouth studied the interactions between dogs and owners, they found canines were more expressive when their human companion was looking at them.

Dogs really do turn on the puppy eyes when humans look at them, according to researchers studying canine facial expressions.

The dogs were all "family dogs" with "typical" training backgrounds for pets, and went back to their homes when their part in the study was over.

"This is a delightful finding that provides more evidence of how dogs draw us closer to them with their eyes", Dr. Hare said in an email.

The recordings were then examined by the team frame by frame to determine changes in the facial muscles of the canines. Each dog was tied by a lead a metre away from a person, and the dogs' faces were filmed throughout a range of exchanges, from the person being oriented towards the dog, to being distracted and with her body turned away from the dog.

The results reveal that the pooches produced far more facial expressions when the human was facing the dog, than when they turned away - in particular, the animals were more likely to show their tongues and raise their inner eyebrows.

Whether or not food was present only had a very minor effect on the dogs' expressions, even though food is known to be exciting for dogs. Scientists modified facial movement tracking technology called FACS - originally designed for human faces - to record changes in each dog's expression.

The study suggested doggy expressions were not simply the result of internal emotions, but could be a mechanism of communication. A 2013 study showed that shelter dogs who made the sad puppy expression more often found new homes faster, suggesting that making that face gives dogs an advantage with humans.

Domestic dogs have lived alongside humans for 30,000 years, she noted.

It's not clear whether the dogs understand what they're doing, whether the behaviour has been bred into them and is "hardwired", or whether it is a learned response from viewing other individuals' expressions.

However, the team stressed the research does not shed light on what the dogs might be trying to communicate, or whether the movements are intentional. I mean, I think most of us assume that they are, especially those of us who think our dogs are basically human; but science has long suggested that animal facial expressions are inflexible and involuntary displays of emotional states rather than active attempts to communicate.

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