Angry human faces trigger mouth-licking in dogs

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Dogs communicate constantly through a combination of olfactory, visual and vocal cues.  Whilst some behaviours such as barking are obvious, some of the more subtle signs that a dog is feeling uneasy such as mouth-licking, yawn or a head turn, might be missed or misinterpreted (depending on the context to which these occur).  Now a study from Albuquerque et al. (2017) has highlighted how the instances of mouth-licking in dogs (which, typically, occurs in response to food or uncertainty) is triggered by angry human faces; indicating mouth-licking is linked to dogs’ perception of negative emotions.

studyThe researchers presented 17 dogs of various breeds with a pair of grey-scale face images of unfamiliar humans or dogs with positive (happy/playful) and negative (angry/aggressive) facial expressions (see image right).  These images were paired with an audio from the same individual (positive or negative vocalisation) or a neutral sound.  The scientists observed the dogs’ spontaneous behaviour in response to the images and sounds, finding that mouth-licking only occurred when the angry human faces were presented, thus is used as a signal to try to communicate with humans in response to visual cues of anger.  Although a small sample size, this study suggests negative emotional visual stimuli, such as angry human faces, is perceived as aversive by the dogs.  As the first domesticated animal, living with humans for tens of thousands of years, it is likely that such communicative skills and perception is a result of evolution.  The adaptive value being that individual recognition plays an important role for group maintenance and enables one to predict another’s behaviour – vital for avoiding conflict.  For example, it has been argued that working dog breeds have been selectively breed for their ability to read human communicative signals, including visual ones.  This study adds weight for greater understanding and awareness of the effect our own behaviour and emotions can have on our pets.
Albuquerque, N., Guo, K., Wilkinson, A., Resende, B., and Mills, D.S. (2017P ‘Mouth-licking by dogs as a response to emotional stimuli.’ Behavioural Processes 146 pp. 42-45

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