Between people, a kiss on the mouth or cheek is a clear signal of warm feelings. But what happens in a dog’s brain when he plants a slobbery lick on someone’s face or hands? There is no definitive answer, although experts in the field of dog cognition have theories.
“If we want to reduce it to one thing, it is communication,” says Ellen Furlongassociate professor of psychology and neuroscience at Transylvania University in Kentucky, where she studies dog behavior. Dogs are very social and well attuned to people. When a puppy communicates with you, it is often for a purpose. “But there are a lot of different things [dogs might be] communicating through a lick,” she adds.
To discern the intent and meaning behind a dog’s actions, “I always suggest that people look at the whole context,” says Furlong. For example, if a familiar dog approaches you energetically, with repeated licks and a loose “wiggling” posture, a lick to the face or hand is likely an expression of greeting or enthusiasm.
Likewise, it may be “an attempt to create a bond or reaffirm a bond,” suggests Zakaria Silvera professor of psychology at Occidental College where he directs the Dog Intelligence Lab. Arousal and overstimulation likely play a role, he adds. “Dogs lick things when they’re excited,” says Silver. Although he points out that most dogs don’t lick casually, and that, anecdotally, “the behavior is disproportionately directed toward people they are familiar with.” If a dog doesn’t greet everyone with the same licks, the action probably has a social meaning: it strengthens relationships between the packs.
There may also be a social hierarchy, as in dogs sometimes one animal will briefly lick another as a show of respect and pre-emptive appeasement. Puppies are more likely to lick older dogs, Furlong says. “It’s like, ‘Hey, you’re the boss, and I know you’re the boss,’” she says. Also in interactions between humans and dogs, the gesture can carry an aspect of reconciliation and submission, depending on the situation.
But other kisses may not be so conciliatory. A lick “can communicate that they are looking for closeness and affection, or they can communicate the exact opposite: that they want some distance and space,” notes Furlong. The “tick to turn down,” she says, is a known behavior among dog researchers and trainers that indicates a pet is trying to redirect someone or escape unwanted attention. A few perfunctory licks on the face or hand, combined with signs of stress such as a stiff body, attempts to turn or walk away, and visible whites of the eyes are all signs of rejection rather than greeting.
“People miss a lot in their dog’s behavior,” she says. “I think we are very good at noticing signals that a dog is happy and often miss signals that dogs are stressed or seeking withdrawal.”
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And if we go one level deeper, even the seemingly cheerful licks can be more nuanced than just a dog’s friendly hello. Behavior is complicated and often determined by multiple factors, Furlong says. In addition to enthusiastic greetings, there may also be a component of curiosity or even taste involved in licking, especially after a dog and its human get together after a while. ‘They lick to taste things. They may lick to explore. They might be licking because you’re coming home from a run and you’re feeling really salty,” she says.
Among wolves, the wild ancestors of our pets, these will often be puppies lick their mother’s face when she returns to the lair, begging for regurgitated food. Some canine cognition researchers, such as Alexandra Horowitz, professor of psychology at Barnard College, interpret domestic dog licking through the same instinctive lens. “Licking your dog when you come home is definitely a greeting. They’re happy to see you, but it’s also a bit of a request for what you just ate,” Horowitz explained in a CBS Morning appearance in October.
Even if we don’t throw up lunch for our furry friends, dogs still get something to lick us. First, there’s the unintentionally reinforcing feedback of squeaks, pets, and squirming that an onslaught of fervent canine kisses typically produces in a human recipient. “We have such strong reactions to it,” Furlong says. Considering that attention is exactly what a tongue-happy dog is looking for, that overreaction likely encourages more and future licking, she says.
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Another bonus for dogs: Licking relieves stress, says Furlong. Dogs will repeatedly lick surfaces (or their own paws) to soothe themselves when they’re not feeling well, she says. licking animal wounds. And at least one Study from 2014 found that licking, along with other forms of “affiliative behavior,” increases levels of oxytocin in dogs, a hormone associated with social bonding and positive emotions. Some online sources further claim that licking releases endorphins such as dopamine in the brains of dogs – activating the classical neural reward system.
So there you have it. Why do dogs lick? Ultimately, “we don’t know,” Silver says, because the question hasn’t been well studied. To get a firm answer or rule out any of the above hypotheses, researchers would need to conduct empirically controlled experiments “where we see exactly when dogs lick people and in what context,” he explains. Instead of definitive statements, we have “informed guesses,” he adds.
Yet the research is Silver has Research has shown that dogs are deeply attached to their owners and are aware of subtle social cues. A August 2023 study that he co-authored, found that dogs were friendlier to strangers who helped their owners with a task than those who did not. “Dogs are really involved in what the most important people in their lives are doing… They may be a little more sensitive to social relationships than we previously thought,” he says. If dogs care enough to observe our human-to-human interactions and adjust their behavior accordingly, then you can rest assured that their kisses are not without consideration.
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