I’m often amazed by how sensitive my dog Brodie is to my mood. When I’m feeling happy or acting in any way playful with the other humans in our house, Brodie races over with a big smile, and usually a toy for me to pull on.
On the other hand, if I’m angry or a little sad, Brodie is more likely to offer me his cute “sad face” and a lick or two (common among dogs as a gesture of appeasement).
He even seems to know when I’ve been working too long and need a puppy break!
Clearly, our dogs are really good at knowing what we’re feeling and responding accordingly. But how do they do it? What gives us away? The answer is a fascinating look into the world of cross-species communication.
Dogs are both like us and very different. Like humans, they are highly social, and their ancestors evolved sophisticated systems for communicating amongst themselves long before the first wolves wandered over to one of our campfires. Part of the reason they were so successfully domesticated is that they were already shaped by a social environment very similar to our own, and they were good at communicating and reading emotional cues.
But of course, dogs and humans are different too. We use language and our faces to do most of our talking, while dogs make much more use of body posture, ear and tail position, and even scent. I’m the first to admit Brodie has a cute and expressive face, but he can’t match a human for the sheer number of facial muscles (about 30-40, depending on how you count them) and distinct facial expressions (hundreds at least, maybe thousands).
Given that dogs are great at reading emotions but are built quite differently from humans in how they express their feelings, how do they do at reading human faces? It turns out, pretty darn well (though again, not as well as another human would). Several scientific studies have found that dogs can recognize individual humans and that they can distinguish between basic facial expressions, such as anger or happiness, just by facial features. They can even identify happy or sad faces when they only see part of the face, so we know they can isolate features, like eyebrows and mouths, and recognize the way these features each look as part of an overall expression of one emotion.
Dogs do run into some limitations when reading our faces, though. Some studies find that dogs are better at reading the expressions of their owners, and they can get confused when looking at a stranger, especially a person of a different gender. And while they can distinguish different facial expressions, it isn’t entirely clear if they know what each one means. They seem to prefer happy faces to sad ones, which suggests they might be able to understand who is likely to give them a treat and who might be more likely to yell “Bad dog!” at them. But they probably can’t recognize wistful nostalgia or a “just kidding” wink and nod.
Despite these limitations, though, dogs have a lot of other ways to figure out what their humans are feeling. Our posture and movements, tone and volume, and even the words we say probably help a lot in making our dogs the super sensitive readers of human emotion they are. After all, for most of them, figuring out what mood we are in is crucial to doing their job. Brodie isn’t going to be chasing off any predators or bringing me some wild-caught dinner any time soon, but he does a great job at being a playmate and a source of comfort when I need it!
Check out some of these clever studies looking at what dogs can understand about human faces. The last one is also a cool insight into how domestication has changed the anatomy of dogs to make their own faces more expressive!
Racca A, Guo K, Meints K, Mills DS (2012) Reading Faces: Differential Lateral Gaze Bias in Processing Canine and Human Facial Expressions in Dogs and 4-Year-Old Children. PLoS ONE 7(4): e36076.
Corsin A. Müller, Kira Schmitt, Anjuli L.A. Barber, Ludwig Huber. Dogs Can Discriminate Emotional Expressions of Human Faces. Current Biology. Volume 25, Issue 5:2015. https://doi.org/10.1016/j.cub.2014.12.055.
Kaminski J, Waller BM, Diogo R, Hartstone-Rose A, Burrows AM. Evolution of facial muscle anatomy in dogs. Proc Natl Acad Sci U S A. 2019 Jul 16;116(29):14677-14681. doi: 10.1073/pnas.1820653116. Epub 2019 Jun 17. PMID: 31209036; PMCID: PMC6642381.