The reason that your pooch is licking its mouth might not be for the reason you think. New research out of the United Kingdom and Brazil suggests that mouth-licking behavior in dogs represents an attempt to communicate with humans, in response to particular human facial expressions, reports Phys.org.

Which facial expressions? Researchers found that mouth licking in domestic dogs is correlated with visual cues of anger. They're likely licking because they think you're angry. It's a finding that might make you reconsider your demeanor when you interact with your pet.

For the study, scientists examined the behavior of dogs in response to emotionally significant images and sounds. Images included examples of facial expressions by both humans and other dogs; sounds included auditory expressions of emotions. Interestingly, the dogs overwhelmingly used mouth-licking in response to the human facial expressions of anger.

"Mouth-licking was triggered by visual cues only (facial expressions). There was also a species effect, with dogs mouth-licking more often when looking at humans than at other dogs," said lead author Natalia Albuquerque from the University of Sao Paulo. "Most importantly, the findings indicate that this behavior is linked to the animals' perception of negative emotions."

In other words, mouth-licking appears to be a form of communication aimed specifically at humans who have angry facial expressions. The dogs did not, however, lick when they heard angry human voices, which is telling. This means that dogs are using visual cues to respond to visual cues alone; they are using their own facial expressions as a response to ours.

Researchers speculate that this behavioral trait may have been selected for during domestication. The study adds to a growing heap of evidence suggesting that dogs are highly attuned to human emotions and human communication. It also shines new light on the complicated and often overlooked emotional world of our furry companions, and proves that they might be more tuned in to us than we are to them.

"Humans are known to be very visual in both intra and inter-specific interactions, and because the vision of dogs is much poorer than humans, we often tend to think of them using their other senses to make sense of the world. But these results indicate that dogs may be using the visual display of mouth-licking to facilitate dog-human communication in particular," explained co-author Daniel Mills of the University of Lincoln.

The study was published in the journal Behavioural Processes.