Why do dogs smile with their teeth? We are so used to seeing people smile, that when dogs pull their lips back and expose their teeth in a non-threatening manner, we assume that they must be smiling.
Dogs and humans share a special bond that dates back many thousands of years, there's no bones about that, but can it be that somewhere throughout this co-evolution timeframe dogs may have picked up this behavior from humans and used it in a similar fashion? As with many things dogs, one must take a critical view before drawing conclusions provided by anthropomorphic assumptions.
The Human Smile
What's in a smile? The language is universal, being widely recognized in people of different cultural and social backgrounds, the corners of the mouth stretch, the muscles at the corner of the eye contract, dimples form and the face assumes an overall joyful, happy expression.
We use this expression almost daily to denote affiliative feelings to co-workers, clients, friends and families. The expression may be used to show a vast array of pleasant emotions such as joy, sociability, happiness, pleasure or amusement.
A Look Back
How did the human smile evolve to what it is today? Primatologist Signe Preuschoft, after analyzing ancient fossilized skulls of primates, estimates that the human smile must date back 30 million years or more.
More than a smile, back then, it was a fear grin, a silent, clenched teeth, facial expression used by our closest biological relatives,monkeys and apes, as a way to communicate they meant no harm to predators.
Theory has it that this signal of appeasement may have evolved from a no-hostility intended display into one of friendliness. Lead researcher Dr Bridget Waller, of the University of Portsmouth seems to agree. She claims that the smiling signal primates use where they show their "sparkly white teeth," is believed to be the ancestor of human smiling.
Back to Dogs
When dogs "smile" with their teeth, they are likely exhibiting what is known as a "submissive grin." A few years ago, a video called "Denver, the Guilty Dog" went viral. The video portrayed a dog who was grinning submissively, when the owner asked him if he "ate the kitty treats." Clearly, this dog's grin, which occurred after considerable prompting (or pressure) from his owner had nothing to do with guilt, explains Patricia McConnell in her blog "The Other End of the Leash." Just as in the fear grin, in the submissive grin the dog retracts his lips horizontally, exposing the teeth.
This behavior is intended to pacify or appease, explains Dr. Bonnie Beaver, Executive Director of the American College of Veterinary Behaviorists and President of the AVMA if her book Canine Behavior: Insights and Answers.
People sometimes confuse the submissive grin with aggression, when in reality the dog is attempting to communicate the exact opposite of aggression, explains Dr. Deb. In a dog displaying a submissive grin, the accompany body language often includes flattened ears, lowered head, wagging tail, squinty eye along with an overall soft body posture. This posture may help distinguish a submissive grin from a defensive or offensive snarl where the fangs are exposed. Dog owners who are uncertain though, should consult with a dog behavior professional for help and advice.
Smiles Across Species
The bared-teeth fear grin or grimace has been reported in several mammalian species from canids to primates. However, its communicative function may broadly differ among different species. In wolves, for example, the ‘submissive grin’ is used by cubs and subordinates when they are actively greeting adult conspecifics, or humans, explains M. W. Fox in his research paper A Comparative Study of the Development of Facial Expressions in Canids; Wolf, Coyote and Foxes, 1969.
Among primates, the grin may have different meanings depending on species and type of social organization. In macaques, it signals submission or rank recognition; whereas, in Gelada baboons and chimpanzees it has appeasing functions meaning they intend no harm and there's no risk of aggression.
These descriptions across different species may appear different, but they seem to share a common evolutionary root, suggest Lisa A. Parr and Bridget M. Waller in the paper Understanding chimpanzee facial expression: dog"smile"insights into the evolution of communication. One may therefore wonder, if the human smile evolved from the fear grin to a more sophisticated form, can it be that the submissive grin in dogs simply didn't have an opportunity to evolve?
A Trained Response
So what about those dogs who can smile with their teeth on command? We sometimes may stumble on videos where dog owners ask their dogs to smile and their dogs promptly respond by showing a flashy smile. The dog"smile" in this case may look quite genuine, how do they do that?
In this case, the dog was likely trained to smile on cue using a training method known as capturing, where spontaneous behaviors are reinforced as they occur.
The dog may have been exhibiting a submissive grin or may have pulled the lips back keeping the mouth slightly open as the owner gave an "oh, that feels so good" belly rub and the behavior was repeatedly reinforced.
Other Forms of Smiling
While a submissive grin is a far cry from our form of human smiling, there are other forms of "smiling" dogs may engage in. Ask dog owners and they'll likely say "of course dogs smile!" When a dog's eyes are bright, the tongue is hanging out and the dog is panting with a happy expression on his face, the dog may be getting quite close to "smiling" or at least is giving signs of enjoying life.
When dogs engage in activities they love, we can tell they are "smiling" with their eyes as their bodies quiver in anticipation. While dogs may not smile like we humans do, they sure seem to be enjoying life to the fullest when they wake up eager to start the day and we sure can learn a whole lot from them!
Did you know? Smiling is something humans do not need to learn how to do, it's a preprogrammed behavior. Kids born blind will never see anybody smile their whole lives, yet, they will smile in the same circumstances just as sighted people, points out Frank McAndrew, professor of psychology at Knox College in Galesburg, Ill. who has conducted extensive research on facial expressions.