By Dr. Becker
Have you ever yawned and noticed your dog yawned immediately after? It likely wasn't a coincidence. Like chimpanzees, dogs often "catch" human yawns. That is, they display what's known in the scientific world as "contagious yawning" or yawning triggered by perceiving others yawning).1 Long thought to only occur among humans and chimpanzees, it was 2008 when research first demonstrated contagious yawning between dogs and humans.
In that study, 29 dogs observed a human either yawning or making other mouth movements that served as the control. Almost all of the dogs (21 of them) yawned when they saw a human yawn, while the control mouth movements had no influence on yawning in the dogs.2
It was a remarkable study, in large part because yawning in response to someone else's yawn is thought to show a capacity for empathy.3 Even the journal Frontiers of Neurology and Neuroscience described contagious yawning as "a primitive expression of social cognition, namely empathy."4
Contagious Yawning Might Help You Bond With Your Dog
It's unclear exactly why people and animals yawn (virtually all vertebrate species yawn spontaneously). One theory is that yawning heightens arousal, even giving your brain a jolt similar to a dose of caffeine.5,6 It's possible, then, that contagious yawning between dogs and people may facilitate a closer bond, even helping to open up communication. According to a study in Biology Letters, "Since yawning is known to modulate the levels of arousal, yawn contagion may help coordinate dog-human interaction and communication."7
Another study, this one published in Animal Cognition, took it a step further, looking into whether dogs' contagious yawning is really socially driven. They tested whether just the sound of a human yawn would trigger yawning in dogs, which would mean the yawn was triggered without a social or emotional influence. However, they found that dogs do indeed catch human yawns and, further, they yawned more upon hearing familiar yawns than unfamiliar yawns.
"Although not allowing for conclusive inferences about the mechanisms underlying contagious yawning in dogs," the researchers wrote, "this study provides first data that renders plausible empathy-based, emotionally connected, contagious yawning in these animals."8 A separate study also found dogs yawned more often when watching their owner yawn (as opposed to a stranger), which suggests "the contagiousness of yawning in dogs correlated with the level of emotional proximity."9
Dogs May Also Yawn When They're Stressed
Dogs may also yawn as a calming signal, which describes a method of communication used to promote peace and stave off aggression within the pack. Most humans miss these subtle cues from their dogs, so if you notice your dog yawning out of the blue, it could be a sign that he's feeling stressed or anxious.
In times when your dog is stressed — at the vet's office, when a stranger walks directly toward him, when there's yelling or even when there's positive stress, such as anticipation of a walk — you can try to calm your dog by sharing a calming signal such as yawning as well.
What Other Species 'Catch' Yawns?
Contagious yawning has been used to test empathy in chimpanzees. One study showed the chimpanzees displayed contagious yawning in the presence of familiar chimpanzees and both familiar and unfamiliar humans (probably because they were raised at a primate research center and were therefore used to humans).10 Another study of gelada baboons similarly found contagious yawning occurred between individuals, especially those that were socially close.11
As research into contagious yawning grows, it seems the capacity for empathy may exist in a number of species. A 2014 study published in PLOS One found, for instance, that wolves are also capable of yawn contagion and the frequency increases depending on the level of emotional proximity.12 Interestingly, female wolves yawned faster in response to the yawns of their close associates, which suggests the females may be more responsive to their social stimuli.
Even budgerigars (budgies, also known as parakeets) have been shown to experience contagious yawning, which was the first evidence of the phenomenon in a non-mammalian species.13 The birds yawned three times more often in a five-minute period when they could see each other than when they could not. In the second experiment, the budgies were shown video of another budgie yawning. The birds yawned twice as often when shown the video clips.
A 2014 study published in PLOS One also found that wolves are capable of yawn contagion and the frequency increases depending on the level of emotional proximity.14 Interestingly, female wolves yawned faster in response to the yawns of their close associates, which suggests the females may be more responsive to their social stimuli.
Earlier this year, sheep were also found to experience contagious yawning,15 which suggests contagious yawning may occur in far more species than are currently recognized. While the underlying reasons for yawn contagion are still being explored, keep a close eye on your dog the next time you yawn. If he yawns in response, take it for what you will, but it's most likely a sign that you're closely connected.