A study has recently revealed that domestic dogs lick faces not simply in response to food or uncertainty, but use it as a signal to communicate with humans in response to their angry faces.
According to researchers from the University of Sao Paulo, Brazil and the University of Lincoln in United Kingdom dogs lick faces as a response to angry human faces.
The dogs were exposed simultaneously to two facial expressions (one positive and one negative from the same individual), which were either human or canine, along with a sound, which could be positive or negative from the same species and gender.
Lead author Natalia Albuquerque from the University of Sao Paulo said that mouth-licking was triggered by visual cues only (facial expressions). There was also a species effect, with dogs licking more often when looking at humans than at other dogs.
The findings indicated that this behaviour is linked to the animals' perception of negative emotions.
The researchers believe that this behavioural trait may have been selected during domestication.
The findings suggested that dogs may have a functional understanding of emotional information and greatly increase our understanding of their emotional world.
Co-author Professor Daniel Mills from 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."
The authors concluded that dogs may be using the visual display of mouth-licking to facilitate dog-human communication in particular.
The research appears in the Behavioural Processes journal.