Can humans recognize emotional state in pet dogs by looking at their face?

Facial expressions are regularly used by humans to detect the emotional state of other people. In 1862 Darwin argued that all species can express emotions and that humans could find out emotions in other animals via both their facial expression and body posture. We investigated whether dogs’ emotional state can be identified by humans by only looking at pictures of a dog’s face and whether experience with dogs can affect this ability. To explore humans’ ability to identify dog’s facial expressions, 27 pictures of dog’s face taken from 9 subjects (different breed, sex, age and colour) under three behaviorally defined conditions (food, alone, reunion) were collected. An on-line questionnaire was developed. Participants were asked to assess the emotional state (positive/negative/don’t know) for every picture. The proportion of correct responses was calculated. Kruskal-Wallis and Mann–Whitney U tests were used to identify differences among categories of people with different experience with dogs (owners, professionals, no experience). The questionnaire was answered by 230 participants (females=159, males=47, NA=24). Participants assigned half of the pictures to the correct emotional state, and positive emotions seemed easier to assess than negative one. “Reunion face” was easier to score than “food face”. Differences were found among categories, and dog owners and professionals recognised the dog’s emotional state significantly better than did people with no experience with dogs. No differences were found between owners and professionals. Our participants were able to identify positive emotional state of dogs, with different morphology, by only looking at their facial expression. In particular, “reunion face” seems to be easier to identify compared to “food face”. This ability seems to be affected by individual everyday experience with dogs. Negative emotional state appears to be more difficult to recognize, possibly because the behavioral situation chosen in the present study (“left alone”) is not always linked with an intense negative emotional state. Future studies should address the ability of people to assess negative emotional states using pictures of dogs experiencing a more intense emotions (e.g., fear).