Dogs are adept at conspecific communication – using subtle and fluid movements to influence and read the intentions of others of their own species. But how well can your dog read your face?
Dogs And Communication
We already know, thanks to studies such as those of Csanyi et al., that the ability of dogs to read and interpret the behaviour of humans is superior to any other species, largely due to the domestication and selective breeding process.
Juliane Kaminski and Sarah Marshall-Pescini’s book, The Social Dog, discusses how dogs are able to determine and identify emotion in human voices, and research like Vickie Plourde and Sylvain Fiset’s 2013 experiment ‘Pointing gestures modulate domestic dogs’ search behaviour for hidden objects in a spatial rotation problem’ shows that they can read the meaning of our hand signals and gestures. However, in a new study, Corsin Muller et al. test the theory that dogs can also read human expressions – specifically happy and angry faces.
Of course, there have been many other studies which deal with responses to emotions in animals, but Muller et al. set out to determine whether dogs could read emotion in faces by ensuring that tight controls were in place. This practice excluded the possibility of the dogs responding to salient discriminatory cues (for example, visible teeth), which may have hampered the conclusiveness of previous experiments with similar theories.
Speaking to Decoded Science today, Corsin Muller explained that he and his team of researchers were unsure if any animal would be able to undertake the task of reading human facial expressions, but decided that, if any were to discriminate between the emotions correctly, pet dogs had the best chance.
A long history of domestication and selective breeding means that dogs and humans have been cohabiting for thousands of years. According to researchers such as Gallagher and Tami in their 2009 study ‘Description of the behaviour of domestic dog (Canine familiaris) by experienced and inexperienced people,’ dogs have developed similar cognitive abilities.
Fighting Against Instincts
Muller and his team began by showing the dogs 15 pairs of pictures – half were shown the upper half of the faces, the other half the lower section. Having undergone initial training with the face and back of the head of one person, they were trained further to recognise happiness and anger in the same person, and rewarded when selecting either the angry or happy face on a touch screen.
Upon conducting the next stage of the experiment, the researchers presented the dogs with a combination of images, comprised of both the training face and a new face, and the original half of the face shown in training and the other half from that shown in training for each face.
From the training stage onwards, it was noted that the dogs who were rewarded for touching the segment of angry faces arrived at the learning criterion (touching the image and receiving a reward) at a slower rate than those rewarded for touching the happy expressions, supporting the idea that they react aversively to the negative emotion conveyed in the angry face and, therefore, take longer to make the decision to go against their natural instincts and approach it.
It’s Not All in the Eyes
Interestingly, Muller et al.’s research found that dogs are no more likely to respond to evidence of emotion in human eyes than they are in any other area of the face, contrary to previous research such as that by Sanni Somppi et al. in 2004; Somppi et al.’s studies did, however, support the idea of the importance of human faces to dogs.
Muller explained to Decoded Science that the dogs could determine that smiling eyes meant the same thing as smiling mouths, and that angry eyes meant the same as angry mouths. This ability is crucial to the conclusion that dogs can tell how we’re feeling based on facial expression. He tells us, “Only because the dogs performed very well in these probe trials, even for faces that they had never seen before, we can confidently conclude that the dogs really discriminated the faces based on their emotional expression.”
Implications for Future Research
Corsin Muller confirmed to Decoded Science that it has not yet been determined whether the level of ability in reading human emotional facial expressions could be linked to the amount of exposure to humans dogs have had, and that future research to try and eliminate, or at least decrease, this factor was being considered.
Whilst conceding that dogs who have had limited human exposure would be “hard to find,” Muller feels that future studies with hand-raised, non-domesticated wolves could hold the key to advancing the research. When we asked whether his findings could possibly extend to other domesticated species such as cats, Muller acknowledge it is “anybody’s guess” – this line of research is so new and, so far, unique, that the intricacies of reading heterospecific emotions are only just beginning to be explored.