It’s well established that when a dog licks her lips, it means she is feeling nervous or anxious. (People do it, too.) Now, new research shows that they lick their lips in response to our angry faces. British and Brazilian researchers reporting in the journal Behavioural Processes made the finding when they observed 17 family dogs of various breeds looking at pictures of people with either happy/playful facial expressions or angry/aggressive ones. The dogs licked their mouths significantly more frequently when looking at the bad-mood faces (more than twice as much, on average).
The researchers posit that the dogs may not simply be reacting to our negative emotion but using their own facial gesture to respond to it, that is, to communicate with us that they know what is going on. If that is the case, it is quite remarkable, given that visual cues are particularly salient for people. It would mean that on some level, after millennia of adapting themselves to our environment, dogs have come to understand that a visual cue (as opposed to, say, an auditory or olfactory one) has a reasonably good chance of getting our attention.
The takeaway here, while scientists work to sort it out: even if a dog isn’t directly trying to say something to you when she licks her own mouth in response to your angry or otherwise negative mood, the licking is a sign that she is now stressed. So if you see your dog licking her lips (and she hasn’t just eaten), do a self check — and reassure her if you discover that it’s something about your own affect that is causing her consternation or worry.