You know that sympathetic look your dog gives you when you’ve had a rough day?

Researchers say that dogs may have evolved that expressive look over thousands of years to better communicate with humans. And guess who can’t make that adorable face? Wolves.

Comparative psychologist Juliane Kaminski at the University of Portsmouth in the United Kingdom led a team that included behavioral and anatomical experts in the UK and the United States. Their study was published in the journal Proceedings of the National Academy of Sciences.

Kaminski said there’s compelling evidence that dogs developed a small muscle to intensely raise their inner eyebrows after being domesticated from wolves.


“The findings suggest that expressive eyebrows in dogs may be a result of humans’ unconscious preferences that influenced selection during domestication,” Kaminski said Monday in a statement. “When dogs make the movement, it seems to elicit a strong desire in humans to look after them.”

Dogs that move their eyebrows more would thus have a “selection advantage over others and reinforce the ‘puppy dog eyes’ trait for future generations.”

She said the eyebrow movement also might give people “the illusion of human-like communication.”

Kaminski in earlier research found dogs moved their eyebrows more when humans were looking at them than when they were not looking at them. In that study, she and her co-authors suggested that there was evidence that dog facial expressions “are not just inflexible and involuntary displays of emotional states, but rather potentially active attempts to communicate with others.”

The muscles in the faces of dogs and wolves are similar, except above the eyes. The muscle that allows for dogs to raise their eyebrows was “a scant, irregular cluster of fibers” in wolves, researchers said in Monday’s statement.

Researchers earlier found evidence that dogs raise their eyebrows more when they’re around humans
Researchers earlier found evidence that dogs raise their eyebrows more when they’re around humansUniversity of Portsmouth

“The raised inner eyebrow movement in dogs is driven by a muscle which doesn’t consistently exist in their closest living relative, the wolf. This is a striking difference for species separated only 33,000 years ago and we think that the remarkably fast facial muscular changes can be directly linked to dogs’ enhanced social interaction with humans,” Duquesne University Professor Anne Burrows, a co-author of the paper, said in the statement.


Rui Diogo, a Howard University professor who is also a co-author, said, “I must admit that I was surprised to see the results myself because the gross anatomy of muscles is normally very slow to change in evolution, and this happened very fast indeed, in just some dozens of thousands of years.”

Researchers noted that it’s also possible that humans have a preference for individuals that show the whites in their eyes and that the muscle exposes more of the white part of the dogs’ eyes.

One dog species did not have the muscle, the researchers said: The Siberian husky, which is one of the more ancient breeds. (Just in case Snowflake is staring at you right now.)

Not interested in making friends. A gray wolf in Minnesota.
Not interested in making friends. A gray wolf in Minnesota.Dawn Villella/AP/File/Associated Press