When a dog licks his chops, it doesn’t necessarily mean he’s got his eye on that botched pizza you just had delivered. More likely, he’s reacting to your reaction that they screwed up your order.

Because you plainly told them, “No Anchovies.” And now you’re plainly peeved.

According to a new study just published in the scientific journal Behavioural Processes, your dog may be licking his lips in an attempt to calm you down. That’s the conclusion of researchers at the University of Sao Paulo in Brazil and the University of Lincoln in the United Kingdom who teamed up to figure out how dogs react to emotionally significant images and sounds.

In the study, researchers showed 17 dogs two photos of the same person. In each photo, the person wore a different expression, one angry, the other smiling. In most cases, the dogs responded to the angry expressions by licking their own mouths. The dogs were also shown photos of other dogs, both happy and angry, and exposed to positive and negative sounds.

The sounds didn’t make much of an impression on the dogs.

“Mouth-licking was triggered by visual cues only,” said lead author Natalia Albuquerque, a researcher at the University of Sao Paulo.

The photos of other dogs didn’t make much of an impression, either.

“There was also a species effect, with dogs’ mouth-licking more often when looking at humans than at other dogs,” Albuquerque noted. “Most importantly, the findings indicate that this behavior is linked to the animals’ perception of negative emotions.”

Previous studies have shown that dogs mouth-lick as a response to stress, but this is the first study to indicate that mouth-licking might be a dogs’ emotional response to observing a specific emotional response in humans.

Specifically, anger.

The researchers point out that facial communication plays a crucial role in the social interactions of several animal species, and rapid discrimination between positive and negative facial expressions may be critical to their social survival. And that this particularly true for domestic dogs who live in mixed species groups with humans, who rely extensively on visual signals for communication.

Albuquerque and her team say their new findings further support the idea of emotional communication between dogs and humans.

Their findings also support several recent other studies that suggest dogs may have a functional understanding of emotional information. A study published just last month, for example, found that dogs really do make “puppy dog eyes” when they know people are watching them.

In this case, when your dog licks his mouth, he may actually be trying to tell you something.

Like, “Dude. Chill out. It’s only a pizza.”

Photo credit: © iStock/canbedone