Are Dogs Really Smiling at Us?

The dog’s mouth opens wide, her lips pull up at the corners, and her tongue lolls out. Most would look at this face and see an unmistakable grin. But is that really what’s going on here? Do dogs use this expression in the same way as people, to convey their joy, pleasure or contentedness?

In other words, are dogs really smiling at us?

The answer has roots in our 30,000-year history of keeping dogs as domesticated animals. Thanks to that history, humans and dogs have developed a unique bond, which has also made dogs very useful subjects for the study of communication. “Studying dogs is a really unique opportunity to look at social communication between species,” said Alex Benjamin, an associate lecturer in psychology, who studies dog cognition at the University of York in the United Kingdom.

Most of this research also reinforces the idea that the communicative bond we share with dogs is unique. For instance, researchers have found that dogs embrace the human gaze and use eye contact in a way that few other animals do.

A study published in the journal Current Biology tested how wolves and dogs would respond to the impossible task of opening a container to get at some meat they knew was within. The researchers found that while the wolves would simply stalk off when they discovered they couldn’t open it, dogs would turn around and give humans a long, inquiring gaze — suggesting that these animals knew a person could help them complete the task.

Another study, published in the journal Science, found that both dogs and humans experience an increase in levels of oxytocin — a hormone that plays a role in social bonding — when they lock eyes with one another. Even more intriguing, dogs that sniffed oxytocin would then spend more time staring at humans.

“[A shared gaze] is the fundamental mechanism for cooperation if you think about it,” especially if, like dogs, you can’t rely on spoken language, Benjamin told Live Science. Humans may have bred this trait into dogs over the course of their domestication, she said. “Dogs that look at us are much easier to cooperate with and train. So, it is possible that some unconscious or conscious selection may also have led to the behaviors we see today.”

In any case, it’s clear that eye contact is important to dogs as a way to intentionally gather information and communicate.

But what about the expressions that cross their faces? Do these have any relevance to humans — and do dogs use them to communicate with us?

That question is intriguing, said Juliane Kaminski, a reader in comparative psychology at the University of Portsmouth in the United Kingdom, who studies dog cognition. She said she’s especially interested in one particularly adorable expression in dogs: the inward raising of the brows that produces what’s known as “puppy dog eyes.”

For her research, Kaminski and colleagues visited a dog shelter, where they used something called a facial action coding system (FACS) to measure the minute facial motions dogs made while they interacted with people. Afterward, the researchers kept track of the time it took for each dog to get adopted. The scientists discovered that “the more the dogs produced that movement [puppy dog eyes], the quicker they were rehomed,” said Kaminski. No other behavior the researchers analyzed had as strong an effect. [Is a Dog’s Mouth Cleaner Than a Human’s?]

Next, Kaminski wanted to find out if this behavior was intentional. “Have [dogs] either understood or learned that if they produce that movement, humans will do something for them?” Kaminski said. So, she set up another experiment, in which dogs were exposed to humans who either did or didn’t offer food. If dogs knew the power of their sorrowful gaze, it would follow that those presented with the possibility of a snack would use it more often to get what they desired.