A Japanese scientist has shown that dogs "cry" and shed "happy tears" when their owners return home.
MirrorOnline reports the new study, published in journal Current Biology, has discovered has proven what every dog-lover will no doubt have hoped - and that our dogs are delighted when we come home to them. The research took place at Azabu University in Japan after scientist Professor Takefumi Kikusui noticed his pet appeared to tear up when she nursed her puppies.
Professor Kikusui explained that canines produce tears, but they don't fall like humans' do - so he was investigated how their emotions interact with the physical suggestion of tears. He said: "That gave me the idea that oxytocin might increase tears."
Prof Kikusui followed this up, and found that dogs had more tears in their eyes than normal when reunited with their owners, and their base level of tears didn't change when they met someone they didn't know. When the researchers added oxytocin to the dogs' eyes, they filled up with tears too, supporting the theory that the release of oxytocin causes dogs to produce tears when they reunite with their owners.
It was already known that the hormone is released in dogs and their owners when they play. The Japanese team also asked people to rate pictures of dogs' faces with and without artificial tears in them, and people loved the teary-eyed pets more.
Prof Kikusui, who was surprised by the results, explained: "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 added: "Dogs have become a partner of humans, and we can form bonds. In this process, it is possible that the dogs that show teary eyes during interaction with the owner would be cared for by the owner more."
The study, published in the journal Current Biology, showed dogs shed tears in happy situations, but Prof Kikusui and his team have yet to test out the impact of any negative emotions. The research team are yet to discover if dogs cry when they are reunited with other dogs - but are looking ahead to investigating if dog tears have a social function in the canine world.
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