Dogs lick their mouths to communicate with angry humans, study finds

LINCOLN, England — If your dog has ever seemed to lick his chops when you’re angry, it’s not out of malice, a new study finds.

Researchers at the University of Lincoln in England and the University of Sao Paulo in Brazil examined domesticated canines that were either exposed to aural or visual emotional cues, hoping to determine whether mouth licking — typically thought to be in reaction to hunger or uncertainty — held any undiscovered communicative significance.

The researchers’ experiment simultaneously exposed dogs to two stimuli: a pair of images depicting a given human or canine displaying positive and negative facial expressions, along with a corresponding sound that either carried a positive or negative tone.

The team monitored each dog’s reaction, particularly noting when the moments they’d lick their mouths when observing the images.

“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,” explains lead author Natalia Albuquerque in a news release. “Most importantly, the findings indicate that this behaviour is linked to the animals’ perception of negative emotions.”

In other words, man’s best friend has seemed to earn his esteemed moniker — he only wants to learn more about your blues and frustration.

Importantly, the researchers believe that this learned trait is only found in dogs that have already been domesticated, which emphasizes the importance of teaching and training a dog early on.

Previous research has suggested that dogs are able to process complex emotional expressions, but this study increases human knowledge of the extent to which they are able.

“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,” says Daniel Mills, the study’s co-author. “But these results indicate that dogs may be using the visual display of mouth-licking to facilitate dog-human communication in particular.”

The researchers published their findings in the Jan. 2018 edition of the journal Behavioural Processes.