Dogs and humans have been spending time together for anywhere from 18,000 to 32,000 years according to The Scientist. With a relationship that old, it's no wonder dogs are considered man's best friend. The dogs we spend time with seem to instinctively know all kinds of human behaviors, so it would only make sense that they evolved to understand that kissing is a sign of affection right? As it turns out, kisses are actually a reasonably new human behavior so our pups don't instinctively recognize them.
Do Dogs Know What Kisses Are?
The history of kissing
As the Woof Report explains, dogs instinctively understand pointing and head-turning. To understand why dogs haven't evolved to recognize kissing the way they've learned to identify what other human expressions means, you need to understand the surprisingly modern history of the human kiss. As the BBC points out, while most people from Western cultures believe that kissing is a universal human trait, you may be surprised to learn that more than half of all cultures do not kiss. This means kissing is not an innate human behavior, but a learned one.
And this learned behavior wasn't even learned until relatively recently in the history of mankind. In fact, while our species is anywhere from 200,000 to 350,000 years old according to Britannica, the oldest documented record of someone kissing is only 3,500 years old. And, in fact, romantic kisses fell out of favor after the fall of the Roman Empire, according to Psychology Today, and didn't re-enter Western culture until the 11th century, meaning most of those cultures that even do kiss today have only been doing so for around 1000 years. That's hardly enough time for dogs to have learned to adapt to this specific way of showing affection.
Do dogs ever understand kissing?
Here's the thing, just because dogs don't innately understand kissing doesn't mean they can't learn what it means. Some dogs will pick up this concept more quickly than others says the Happy Puppy Site, especially breeds that can more easily read their owners and understand their unspoken commands, such as golden retrievers or cavalier King Charles spaniels. More primitive breeds, (meaning breeds who have retained more of their original personality despite the generations of breeding) such as huskies, basenjis, or the Mexican hairless according to Innovative K9 Academy, may have a harder time understanding these behaviors.
Though we humans believe these things to be signs of affection, to your pup, kissing your dog on the head or even hugging it can seem like an aggressive act. Watch dogs greet each other and you'll notice they almost always approach each other from the side unless one or both dogs is actively trying to intimidate the other. A lot of people argue "I kiss my dog on the lips and he doesn't mind, so dogs must like kisses." But the reality is that while your dog who has gotten to know you may learn to tolerate or even enjoy this behavior, his instinct says this is a sign of aggression.
Kissing dog on the head
Think about it like this: You might love to get kisses on the lips from your partner or child or to get a kiss on the head from one of your parents. But if a random stranger on the street gave you a kiss, you would feel incredibly uncomfortable and you would not likely feel secure, loved, and safe. While you might like the behavior of kissing if it comes from people you know, in the case of a stranger you'd likely feel angry and threatened and would be likely to act aggressively towards that person. Dogs are the same way only they don't generally feel as comfortable getting kisses from people they love.
So what about dog "kisses?"
Well, when dogs lick one another or their human companions, it's not really kissing, even if that's what we call it. There are a number of different reasons for this behavior, for example, puppies lick their mothers to get them to regurgitate food, which is an ancestral wolf behavior most dogs will grow out of. Licking, like so many other canine behaviors, can be a sign of submission. Dogs might also lick another dog's mouth simply to taste what the other dog has eaten.
Dogs can lick humans for all of these reasons, but they may also do so because they saw that their owner reacted positively to being licked in the past and dogs generally like to do things that make their owners happy. This is particularly true if you gave your dog extra attention, toys, or treats after he kissed you, which will make him kiss you more in the hopes that he will get these same rewards in the future.
Should you kiss your dog?
Ultimately, that comes down to your dog and how she reacts to your kisses, and some dogs will react positively towards them while others will not. In fact, while dogs instinctively don't understand kisses, the Labrador Site reports that a study in 2012 tested the blood of Labrador retrievers and their owners for their levels of oxytocin (known as the love hormone) and cortisol (the "stress" hormone). They then asked the owners to interact with their dogs for an hour before testing their blood for these chemicals again.
The results showed that dogs who had the greatest rise in oxytocin levels were those who were frequently kissed by their owners, indicating that kisses can actually make dogs feel good —as long as they have learned what kisses mean.
How to kiss your dog
If you want to give your dog kisses, you first need to know how your pup feels about them. Learn the signs of discomfort in dogs, which may include things like panting and tail wagging that can often be mixed up with signs of happiness. Specifically, learn how your dog acts when he is anxious, aggressive, or unhappy. Once you can easily understand how your dog reacts when he's happy or not, see how he reacts when you give him a kiss.
If you have a young puppy, giving her kisses from an early age may help her to learn that this behavior is a sign of affection from her owner. If your puppy is older, start slow, approach your dog from the side, and give her a kiss on the cheek. If she responds positively, you might move on to giving her kisses on the top of the head. While you could move on to kisses on the mouth if she does well with head kisses, as USA Today points out, it's really not advisable to kiss your dog on the mouth (or let her lick your mouth) because of all the germs she carries.
If at any point your dog seems uncomfortable or begins to get aggressive, then stop kissing him. You can try again at another time since it's possible that other things made him anxious before your kissing interaction, but if he repeatedly seems uncomfortable with kissing, then stop doing it and just look for other ways to give your pup affection that you both can enjoy.