You are standing at the corner of a busy intersection waiting for the light to change with your dog sitting beside you. People are chattering loudly nearby, and pressing close and suddenly your dog gives a large dramatic yawn. Is he just tired? Somehow this seems unlikely since he was so excited just minutes before when he found out that he was coming on this walk with you.
We know a lot about the functions of many common behaviors: for example scratching relieves an itch and sneezing helps to clear out your nose, however the function of a yawn is still far from clear. The fact that yawning involves a gulp of air led many scientists to think that its function was to replenish oxygen in the brain
, but to date researchers haven't found evidence supporting this idea. Neither does yawning help to wake up a groggy body or brain, which might be a logical guess since yawns occur most frequently when a person is tired. Recent research suggests that yawning may help to cool an overheated brain which is consistent with the fact that yawning is more likely in a warm room.
The clue which indicates that yawning may have communication value comes from the fact that yawns are so "contagious". When one person in a room yawns this is apt to trigger yawning in others that observe the behavior. When several people are present, we are more apt to "catch a yawn" if the person who is yawning is familiar to us. It may take some learning for humans to engage in this behavior since infants and preschoolers don't catch yawns, not even when the yawns come from their own mothers. The critical finding for us is that a recent study by Karine Silva and her associates from Abel Salazar Biomedical Sciences Institute in Porto, Portugal, confirms earlier observations that dogs also catch yawns, not only from other dogs but also from humans, especially humans who are familiar to them.
If a yawn is trying to communicate something, then what is trying to say? Direct observations of canine behavior have shown that dogs that are under stress are more likely to yawn. In dog obedience classes, for example, I have often seen a dog yawn immediately after its master scolded it for something, or gave it a very harsh correction. When training their dogs to sit and stay or lie down and stay, people are often unsure about whether their dogs will remain in place or will break and run toward them (or toward the other dogs) when they move away. For this reason novice instructors often use very harsh and threatening tones, instructing their dogs to "Staaaaaaaay!" using their best imitation of the Voice of Doom. Such a tone of voice implicitly suggests that the dog just might die if he moves from his place. For this reason in a beginner’s class you will see a number of dogs left in a sit-stay position, yawning, while their masters stand across the room staring at them. When the owner is taught to use a more friendly tone of voice for commands, the yawning behavior usually disappears. In this sense, yawning might best be interpreted as "I'm tense, anxious or edgy right now."
One of the most interesting canine uses of yawning, however, is to send a pacifying message. The Latin roots of the word pacifying give us a good indication of the meaning of the word, since it comes from pax, meaning "peace," and facere, meaning "to make." The yawn contains no elements of fear, dominance or aggression. It is the exact opposite of a threat. When a dog is being menaced by another dog's aggressive signals, the target of this display may simply respond with a yawn. While the dog's human companion may view this as a sign of nonchalance or bored confidence, it is, in reality, sending a pacifying message. At the same time, yawning is not a sign of submission. The threatening dog will often break off its aggressive display immediately upon seeing its target yawn. It may even act a bit uncertain or unsure about what to do next, and then may begin to initiate tentative greeting and approach behaviors.
There is another situation where yawning can occur, but in this case it is a pacifying gesture given by a dominant dog. Suppose that a dominant animal is approaching a submissive dog who may be fearfully protecting something like food. In these circumstances the dominant dog may yawn, perhaps as a sign of friendly unconcern. This does seem to have a relaxing and calming effect on the fearful dog.
Dogs also read yawning signals in humans. I was once called upon to be a guest on a television show where we were to discuss the personalities of people who pick specific breeds of dogs. Several people had been asked to bring their dogs so that they could be interviewed about their relationships with their pets and why they chose them. When I was ushered onto the set, three sets of dogs and owners were already seated there. As is typical of such situations, the dogs were a bit fidgety with all the lights, movement and strange people around them. My place on the set was next to the host of the show. On my other side was a woman with a large Rottweiler. As I sat down the Rottweiler began to give a low throaty growl, and curled his lips to show his teeth while staring directly at me. Apparently, he was already uncomfortable in this strange situation, and having a stranger blithely sit so close to him was the last straw. He was now indicating that he wanted me to back away and give him some space. Unfortunately, I could not do that. Even worse, there was only a minute or two before we were supposed to go on air, so there was not time to go through the usual greeting ritual that I use when meeting an unfamiliar dog. Since there were few other alternatives, I simply looked off to the side, breaking eye contact with the dog and gave a large and exaggerated yawn. The dog looked at me and began to blink. I blinked back, and the dog settled quietly down to the floor with its head on my shoe. The threat had been defused.
Since that time I have sometimes used yawning and sometimes suggested it to others when faced with potentially aggressive situations. Generally speaking, a yawn, followed by some other nonthreatening greeting response has caused the dog to which it was addressed to either cease or to tone down its aggressive display. Thus while yawning in public may be viewed as a relatively meaningless (or even an impolite) behavior among humans, it is conversation and conciliation when used by or to dogs.
Stanley Coren is the author of many books including: Born to Bark, The Modern Dog, Why Do Dogs Have Wet Noses? The Pawprints of History, How Dogs Think, How To Speak Dog, Why We Love the Dogs We Do, What Do Dogs Know? The Intelligence of Dogs, Why Does My Dog Act That Way? Understanding Dogs for Dummies, Sleep Thieves, The Left-hander Syndrome
Copyright SC Psychological Enterprises Ltd. May not be reprinted or reposted without permission