Dog owners might tell you their dog understands them better than most people. What they don't know is the dog understands them probably better than even they realize.

Researchers studying canine-human connections have found dogs can "catch" human emotions, and like children, dogs often look into their owners' faces for clues about how to react to people and the world around them; a primitive form of empathy known as emotional contagion.

They also experience the release of oxytocin, one of the feel-good hormones typical of human bonding.

For years it was assumed these developed as an evolutionary necessity, as disagreeable dogs from the time of their genesis from wolves would be selected against by their new masters. But the reality is much more heart-warming than our furry friends' bowing to the whims of simple biological imperatives.

Many factors influence the connection between a dog and their owner, such as the neuronal activity in the pooch's brain, and even changes in human body odor. In a study published this year, it was found that pet dogs and pack-living dogs and wolves had physiological differences when interacting with a closely-bonded human.

The pets released oxytocin, while the pack-living dogs and pack-living wolves did not, even though it was clear they preferred to be with their bonded human, which the researchers suggest means that it's life experience, not breed, that causes this special connection.

Furthermore, some dogs share not only our joy but our fear as well. Looking at concentrations of cortisol, the stress hormone, another group of researchers found that compared with solitary hunting and ancient, wolf-like breeds, herding dogs' cortisol concentrations were correlated with those of their owner.

It's also been observed that dogs react the same way we do when encountering a crying infant: with a mix of submissiveness and alertness, and one study even demonstrated that dogs can synchronize their behavior on the basis of a whopping six human faces: anger, fear, happiness, sadness, surprise, and disgust.

An article in National Geographic details how it could very well swing both ways, as even though dogs' emotional capacities aren't as complex as ours, their rawness in theory could rub off on us.

"I do think we pick up their emotions, too," Marc Bekoff, an evolutionary biologist at Univ. of Colorado, told Nat Geo. "Sometimes it's easier to pick up their fear and stress. However, happy dogs are also easy to read if they run up to you with their tails wagging and their ears are forward, not tucked back."

Cascading effects of joy and stress are plain to see in the world of dog owners. If a dog lunges or growls at something, it can stress or embarrass the owner—signals the dog picks up on, accentuating the stressful encounter.

On the other side of the spectrum, dear friends greeted at the door with kind words can excite a dog, leaping up on the guests' legs despite being trained not to.

Sharing a life and home with dogs for tens of thousands of years has created an intimate connection between our species; an interdependency that has allowed both of us to flourish far more than we could alone.

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