Dogs have long been man's best friend, living as our domesticated companions for as long as 32,000 years. Today, they are one of the most popular pets in the US, found in over 54 million American homes, or about 44% of all households.
And every one of us thinks that our dog is uniquely special and smart. But how much do we actually know about our furry buddies and what is going on inside their heads?
To find out more about our four-legged friends, we spoke to Dr. Brian Hare, professor of cognitive neuroscience at Duke University, author of the book "The Genius of Dogs," and host of the new DogSmarts podcast.
"What really has happened in the last 10 years is that we've learned more about how dogs think than in the previous 100 years," Hare told Business Insider. "There have been a lot of big discoveries ... Dogs are very distinctly different from us genetically, but psychologically, they are more like us than some of our more closely related, more genetically related, primate relatives."
Here are a few of the recent discoveries that Hare and other scientists have made about dogs and what goes on inside their brain:
1. Dogs feel empathy
When you look at your dog and yawn, chances are your dog might yawn too, because dogs, according to a 2008 study published in Biology Letters, can "catch" your yawn. This is called "emotional contagion" and is a basic form of empathy. Previous research has shown that primates could "catch" yawning, but this was the first study to show that human yawns are possibly contagious to domestic dogs as well.
Dogs are believed to empathize with us in other ways, as well. There is research suggesting that they are sensitive to their guardians' emotions and that their behavior is influenced by the expression of these emotions. Another study found that dogs respond in a similar way physiologically and behaviorally to humans when they hear a human infant crying — another example of emotional contagion.
2. Dogs make eye contact
Dogs are the only non-primate animal to look people in the eyes, reports Mic, without misinterpreting what it means.
Wolves, meanwhile, interpret eye contact as a sign of hostility, according to Science magazine.
3. With eye contact, they form a special bond with humans
Eye contact has an important effect on both human and dog brains. "Just by making eye contact with dogs," said Hare, "we have an increase in oxytocin." Oxytocin, sometimes referred to as the "love hormone," plays an important role in attachment forming, bonding, and trust.
Usually, this kind of response — an increase in the hormone to facilitate bonding — occurs only between parents and their children, or maybe romantic partners, Hare explained. This "is the first time that it has been shown that different species, dog and human, can interact and affect the oxytocin loop," he added.
4. Dogs see humans as part of their family.
Recent studies of dogs' brains suggest that not only do they love us, but they also see us as their family, reports Mic. A 2015 neuroimaging study about odor processing in the dog's brain found that when dogs smelled their owner, the "reward center" of their brain (called the caudate nucleus) lit up. Also, the study found that the dogs prioritized the smell of humans over all other smells.
5. And they interact with us as if they were children
Behavioral research has shown that dogs are the only domesticated animals that interact with their humans in the same way that babies interact with their parents. Unlike cats or horses, reports Mic, dogs that are scared or worried will run to their humans for help and comfort, in much the same way a toddler runs to their parents. Cats and horses simply run and hide.
6. Dogs understand gestures, like pointing.
When it comes to understanding gestures, like pointing, dogs and young children start around the same level: if someone points to an object, both will be able to interpret the hand movement and find the object. Dogs are able to divine the meaning behind the gestures and this is something that, according to a 2012 study in PLoS ONE, even chimps failed to do.
Dogs also appear to be able to read more subtle gestures such as social cues, for example using the direction of human gaze, to find hidden food and objects, a task that apes also struggle with, reports The Scientist.
7. Dog brains react to human voices
A 2014 study in the journal Current Biology took MRI scans of dogs' brains while they listened to a variety of different dog and human sounds. The images showed that dog brains have voice areas in the brain, and that they process voices in the same way that human brains do, with a similar part of the brain lighting up at the sound of human voices. They also found that dog brains responded when they heard emotional sounds, such as crying or laughter. These findings might help explain why vocal communication is so successful between humans and dogs.
8. Some dogs can learn new words the way children do
Dogs, like dolphins, apes, and parrots, can learn a series of vocal commands — or words. One dog, a border collie named Rico, knew more than 200 words, mostly the names of toys. What made Rico so special, though, wasn't the dog's ability to know so many words, said Hare. It was how he had learned them. Rico was using a process called "fast-mapping," or inference, which is the same way children learn language skills.
Growing up, children learn words very quickly because if they hear a new word, they can infer its meaning by putting it together with a new object. Rico did the same thing: when scientists asked him to fetch a toy he didn't know the name for, he looked at all the toys in the room and all of them — except one — were familiar to him. Therefore, the new word must correspond to the new toy, so that is the one he picked. "There is no other species on the planet that has come close to doing that," said Hare.
Other dogs, including another border collie named Chaser who learned 1000 words, have also been able to use this same fast-mapping method.
9. And some dogs have the ability to generalize
Today, more dogs have jobs helping humans than ever before, and one of those jobs — being a seeing-eye dog — relies on a dog being able to do one important thing: generalize. In other words, guide dogs have to be able to take what they learn in one specific situation, and apply it to all similar situations. This is why they are picked and the focus of their training.
For example, seeing-eye dogs know how to apply their training about when and how to cross a street and apply it to every street they will ever cross — even if it is a cross-walk they have never been to before.
While not all dogs are the same (and not all have all these abilities), it is still clear that we are getting smarter about how smart our canine friends really are.
Related: Click below for dogs with incredibly expressive faces