Why does my dog yawn when I yawn? What the contagious-yawning studies found

The study that started it was Joly-Mascheroni, Senju and Shepherd, “Dogs catch human yawns,” in Biology Letters in 2008. Twenty-nine pet dogs each spent five minutes with a stranger who caught the dog’s eye and yawned, out loud, over and over. In a second five-minute session the same stranger just opened and closed their mouth without yawning.

21 of the 29 dogs yawned during the yawning session. None yawned during the fake mouth-opening session. The first yawn usually came about a minute and a half in. That was the first evidence of yawn contagion jumping between species, and it made headlines.

The authors were candid about one problem. Dogs also yawn when they are tense, and nobody measured stress hormones or heart rate. A stranger staring and yawning at you could be a little unsettling, and the study could not rule that out.

Two follow-up studies pointed to yes, which is the result most people find charming.

• Silva, Bessa and de Sousa, 2012 (Animal Cognition): 29 dogs at home heard recordings rather than seeing anyone: their owner’s yawn, a stranger’s yawn, and yawns played backward as a control. Dogs yawned to the human yawn sounds and yawned more at their owner’s. Only about 40% of the dogs yawned at all, so the effect was real but not universal.
• Romero, Konno and Hasegawa, 2013 (PLOS ONE): 25 adult dogs, tested at home by a University of Tokyo team, watched both their owner and an unfamiliar researcher yawn or make a silent mouth movement. 13 dogs yawned, more in the yawn condition, and more when the owner yawned. Heart rate, monitored in 21 of the dogs, did not change, which the authors read as evidence the yawns weren’t a stress response.

In people, contagious yawning is stronger between family and friends than between strangers, and it’s been linked to empathy. A familiarity effect in dogs is why researchers floated the idea that dogs share a basic form of emotional contagion with us. The Tokyo team called it evidence that “rudimentary forms of empathy” could be present in dogs.

This is the part most pages skip. Not every lab found the effect.

• Harr and colleagues, 2009 (Animal Cognition): 15 dogs watched videos of people and dogs yawning. Only one dog yawned significantly more at yawns than at open-mouth clips.
• O’Hara and Reeve, 2011 (Animal Behaviour): 19 dogs, owners and strangers, with heart rate and anxiety signs tracked. Five dogs yawned at a stranger’s yawn, but the authors could not confirm contagion and found “no support for empathy-based, emotionally connected yawning contagion.”
• Madsen and Persson, 2012 (Animal Cognition): 35 young dogs. Most caught yawns, but owner versus stranger made no difference.

Some of the disagreement is method: video versus a live person, silent versus noisy yawns, a calm home versus a lab. But it means the familiarity effect is suggestive rather than settled.

Sometimes, and that’s the main rival explanation. Trainers and behaviorists have long described yawning as a stress or appeasement signal: a dog yawns during a tense meeting with another dog, during a training correction, or when a stranger leans over it. The AKC lists stress, defusing tension and contagion all as reasons dogs yawn.

A 2013 study by Aimee Buttner and Rosemary Strasser tested 60 dogs at the Nebraska Humane Society. Across the group there was no contagious yawning. But the 12 dogs that yawned only when a person yawned had cortisol, a stress hormone, that stayed elevated, while the other dogs’ levels dropped. The authors suggested that in a stressful place, a human yawn may push an already aroused dog into yawning.

So the best current reading is that both things happen. A relaxed dog on the couch with its owner may genuinely catch a yawn. A dog in a strange, noisy place may yawn because it is uneasy. Context tells you which.

Watch for yawns that don’t fit the moment. A dog that yawns again and again at the grooming table, in the vet waiting room or at the daycare front desk, when it can’t possibly be sleepy, is often telling you it’s uneasy. Look for the company a stress yawn keeps:

• Lip licking or tongue flicks with no food around
• Looking away, or showing the whites of the eyes
• Ears pinned back, tail low or tucked, a lowered body
• Panting, trembling or whining when it isn’t hot or excited

A yawn on its own means little. A cluster is worth mentioning to the staff. Good daycares watch for exactly these signs during a temperament test, and a good groomer will slow down or take breaks for a dog that shows them. If your dog finds kennels hard, see our guide to boarding an anxious dog.

And when it’s the two of you at home, slow and sleepy at the end of the day, go ahead and enjoy it. A yawn back might just mean your dog is in sync with you.