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.

Dog licking its mouth
Dogs don’t just lick their mouths when they’re hungry. A new study finds that mouth licking is a way for man’s best friend to communicate with angry owners. (Photo from StockSnap on Pixabay)

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.

YouTube video

This video shows a dog licking its lips when the image of an angry female human is shown, suggesting that dogs may have a functional understanding of emotional information. (Video credit: Natalia Albuquerque)

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.


  1. My dog knows many words and gestures to follow my commands as well as using her own gestures to communicate back. I hope they didn’t waste a ton of money examining something obvious in dogs.

    1. They’re applying for a $3 million grant to study whether dogs enjoy chewing bones, and a followup $3 million to determine whether they prefer to greet each other by butt-sniffing, or by texting on a cellphone.

          1. Really? Have you ever actually sniffed a woman’s butt on Friday night in the clubs, when she came right from work and didn’t bother with a courtesy douche or wet towelette pass on her brown hole? One woman told me that she figures by the time the guy gets down that far, he’s so drunk and horny he doesn’t care about the “wind off the sewage plant” odor and a quick squirt of cheap perfume will take care of things.

  2. Curiously it was found that the pictures had the greatest effect immediately after the dogs finished eating or drinking water.

  3. I read an article awhile ago that said that horses lick their mouths in response to humans talking to them, a form of cognition. After that, I noticed that my dog also licks his mouth when I talk to him. I think – to some extent – he’s “thinking” about what I’m saying. Although, he does respond to commands, I believe he’s responding more to the emotional content since my conversation with him is more free-form and not a command. And, I respond to his conversation … like “I gotta’ go boss … NOW!”, but I don’t lick my mouth in response, although I feel compelled to twitch my butt, and walk around in a small circle.

    1. Well that’s fascinating Fruit Season butt that’s not we are talking about here. Move to one of the empty desks at the front of the class here and try and pay attention.

  4. When are leftist tropes like diversity or mass immigration or so-called antiracism ever demanded of any non white peoples anywhere?

    If diversity is such a strength, why are the oh-so-humane left giving this “gift” to European populations Only, when there are so many non white populations in the world that “need” it much more?

    its Anti White

      1. Dogs refuse to assimilate! Send them back where they came from!

        Did you know that on average, their IQs are lower than ours? Human power!!!

  5. I certainly hope that none, NONE, of my tax dollars or anybody else’s for that matter, went for this ludicrous study. A perfect example of why gov’t is too big and should be cut by 10-20%. Ridiculous.

  6. My dog licks his mouth when he knows he’s in trouble. I just point to a fresh puddle that he created in the house, and he droops his head, ears back, and starts the mouth licking. I don’t even scold him. He just knows he is wrong and acts accordingly.

    1. I want to hear about a study that uncovers why dogs will eat absolutely anything, including feces.
      My best guess is that, going back to when we first partnered with “dogs”, they not only served as protectors, hunting partners and companions, but completely cleaned up our “camp sites” so as to discourage predators and other animals from being attracted to them, following and harassing us.

  7. Dogs do a cross lip lick in order to insure their mouths are not stuck together, in anticipation of having to open their mouths to bite, as a preparation to the potential need to be combative. you will see them do this regularly when approached by a dog they do not know, or another animal..

  8. Here’s my troubling take from this: once again because dogs have what scientists consider relatively bad vision, they just assumed that dogs don’t really use their vision much to evaluate their surroundings!! What? Grow up, scientists, you aren’t supposed to “reckon…” you’re supposed to experiment! Dang.

  9. I had an intelligent female Rotty mix. I caught her doing something she knows I don’t like. When I called her out, “Gretel, what did you do?” – she smiled with her eyes closed and bared her teeth slightly. I’ve seen that on dogs who know they’re caught and have the same reaction. I was told It demonstrates a higher level of intelligence. She was incredibly smart and sweet. They know what they’re doing is wrong. Dog are the best!

  10. The dog licking his lips typically means that residue from a substance(s) earlier excreted from his or another dog’s alimentary system and partially consumed by the dog in question remains thereon.

  11. Wow…my dog knew over a hundred English, German and sign language commands. Have to say it’s about time we started training the sentient partner in the relationship a few dog “words”.
    BTW. Most dog owners already knew this.

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