The mouth lick has long been believed to be a response to food or uncertainty, but a new study suggests that it is also an attempt to respond to and communicate with angry human faces.
In the study, animal behavior researchers simultaneously presented domestic dogs with two facial expressions - one pleasant and one angry - made by the same individual, which was either human or canine and of either sex. At the same time, the dogs were exposed to a sound cue - either positive or negative - from the same species and sex.
According to the study's lead author Natalia Albuquerque of the University of Sao Paulo in Brazil, the dogs did not respond to the positive and negative audio cues but showed significant responses to the visual representations of happiness or 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. Most importantly, the findings indicate that this behaviour is linked to the animals' perception of negative emotions."
The researchers believe this aspect of adult dog behavior evolved as a result of the domestication process. This research, when considered alongside previous evidence of the way dogs process and respond to emotional expressions in other individuals, indicates that dogs likely possess a working understanding of emotional information.
Study co-author Professor Daniel Mills of 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."
The study has cast new light on how licking behavior is altered by emotionally significant images. It was published in Behavioural Processes and you can check it out here.
What do you think of this fascinating new insight and new research? Tell us in the comments section!
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