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There’s A Surprising Emotional Reason Why Dogs “Mouth-Lick”

Written by: Dina Fantegrossi
Dina Fantegrossi is the Assistant Editor and Head Writer for HomeLife Media. Before her career in writing, Dina was a veterinary technician for more than 15 years.Read more
| Published on December 1, 2017

A recent study conducted by the University of Sao Paulo in Brazil and the University of Lincoln in the UK has revealed an interesting aspect of canine behavior. The researchers examined dogs’ responses to “emotionally significant” images and sounds and found that the “mouth-licking” often associated with hunger and uncertainty also appears to be used in an effort to communicate with humans they perceive as angry.

The dogs were shown images of faces with positive and negative expressions – one each from the same individual which could be either human or canine of either sex. The scientists also played an accompanying sound which could be positive or negative from the same species and gender.

While the dogs reacted to the negative human facial expressions with mouth-licking, the audio cues of angry human voices did not elicit the same response.

The study’s findings have been published in the scientific journal Behavioural Processes and offer a new glimpse into the emotional world of dogs.

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

The researchers believe this behavioral trait may have been inadvertently selected during domestication. The findings suggest that dogs have at least a functional understanding of emotional information.

Combined with previous evidence of how dogs process emotions in others, this information serves to improve our understanding of their emotional world.

Co-author Professor Daniel Mills of the School of Life Sciences at the University of Lincoln, said:

“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.”


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