Happy dogs are easy to spot. Their tails wag excitedly back and forth, they cover us in sloppy, wet kisses and, sometimes, their whole body shakes with enthusiasm as they roll over on their backs, eager for more attention.

However, according to a new study, your dog might also be capable of crying tears of joy.

Researchers at Azabu University in Japan found that a dog's eyes will well up with happy tears after being reunited with their owners after only five to seven hours.

"We found that dogs shed tears associated with positive emotions," Professor Takefumi Kikusui of Azabu University revealed, as reported by CNN.

"We also made the discovery of oxytocin as a possible mechanism underlying it," Kikusui continued, describing oxytocin as a "love hormone."

The professor's research into dog tears began six years ago when he noticed his poodle's facial expressions while she nursed her new puppies.

According to Fox News, Kikusui said his dog appeared to be crying while she nursed. However, the tears weren't falling like normal tears.

"That gave me the idea that oxytocin might increase tears," Kikusui explained.

A team of researchers studied dogs' tear volumes before and after the pets were reunited with their owners. They ultimately found that the dogs were indeed crying tears of joy.

Kikusui said their findings were surprising but helped validate the belief of a solid emotional bond between humans and our canine companions.

"We had never heard of the discovery that animals shed tears in joyful situations, such as reuniting with their owners, and we were all excited that this would be a world first," he said, according to Fox News.

Now that we are never leaving the house again, have you ever noticed your furry friend crying? Share your story with PopCrush by connecting with us on Facebook or Twitter.

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