If your best friend catches you in a bad mood, they try to console you, give you space to cool off or lick of her own face in an uncontrollable drool?
If your best friend is a dog, this third response can be trusted. Dogs lick their own mouth, nose and cheeks all the time. Certain cuteness obsessed by the Internet communities call it a “mlem”; an animal behavior researchers prefer to call it mouth-licking, and offer a variety of possible explanations for the quirky dogs behavior. Mouth-licking is described as a stress-coping mechanism, a spontaneous display of excitement or a way to communicate, a desire to play with a particular toy or munch a certain treatment.
But according to a new study of the behavior of researchers of the University of Sao Paulo, Brazil, mouth-licking, can actually be one of a dog, the best tools for the reading and respond to human faces — in particular, angry faces. [10 Things You didn’t Know About Dogs]
In the study, the researchers exposed 17 healthy adult dogs to a series of audio and video signals that are both positive and negative emotions. On two screens, the test dogs were given a combination of happy and angry human faces, and happy and angry dog faces with corresponding audio recordings. The researchers documented cases of mouth-licking as each pupper watched the presentation. In the end, they found that only the images of angry human faces proved to be a reliable trigger for mouth-licking.
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“Mouth-licking was elicited by visual cues alone,” lead study author Natalia Albuquerque, a doctoral student in experimental psychology at the University of Sao Paulo, said in a statement. “There was also a species effect, with dogs that mouth-licking is more often in people than other dogs. More importantly, the findings indicate that this behavior is linked to the animals’ perception of negative emotions.”
The researchers found that the dogs responded to the angry-looking human faces with about twice as many mouth-licking as they did when they looked at happy looking human faces, according to the study, which was published yesterday (Nov. 28) in the journal Behavioural Processes.
The impressive emotional intelligence of man’s best friend is not a new story, but these findings could indicate the existence of a more intimate behavioral-evolution of dogs and humans than previously thought. The researchers said that they believe that these mouth-licking property may have occurred during the process of canine domestication, and that it is designed specifically for canines to better communicate with the human inmates.
“Facial communication plays a crucial role in the social cognition of different species and the ability to quickly distinguish between positive and negative facial expressions may be fundamental for the success,” the authors wrote. “This is particularly relevant for the domestic dogs who live in mixed species groups with people, a species that relies extensively on visual cues for communication.”
The new study follows the same team 2016 findings, which suggested that dogs accurately match recorded speech patterns with the corresponding facial expressions. So be sure to laugh the next time you see a mlem; that doggo watching you better than you think.
Originally published on Live Science.