CUBA – JULY 28, 2014: Close up portrait of a cute mongrel pet, a gracious animal in the backyard of the house. … [+]
Oxytocin or the “love hormone” is produced in the hypothalamus of the human brain and is released when we feel connected to other living beings through our ability to develop empathy, love and trust. This hormone is known to play a vital role during childbirth and breastfeeding, and it is also released during intercourse or simple things like hugging or kissing a loved one.
Scientists have discovered that the neurotransmitter oxytocin is not just something produced in the human brain. But when dogs experience positive feelings—such as seeing their favorite person come home—they rejoice at the brain’s ability to release oxytocin and burst into tears.
In a new study published in the journal Current Biologylead author Takefumi Kikusui and colleagues at Azabu University in Japan show how love hormones can make dogs cry when they feel happy or excited.
“When dogs are reunited with their owners, they display highly agreeable behaviors, including staring at their owners, wagging their tails, jumping up, and licking their owners’ faces,” the researchers wrote in the paper. “Physiologically, dogs are Oxytocin concentrations increase during reunion with humans.”
The researchers worked closely with dogs, including a poodle named Kochi, who displayed unbridled joy and excitement after seeing its owner return home after six months away.
In the first experiment, the researchers measured the amount of tears the dogs made in a normal home environment, when their respective owners were present, and during the first 5 minutes of reuniting the dogs after being separated from their owners for up to 7 hours.
“After being separated from their owners in a dog day care center, dogs secreted greater tear volumes when reunited with their owners than when reunited with familiar non-owners, and significantly greater tear volumes when reunited with their owners than at baseline,” the researchers observed .
Once this was established, they investigated the role of oxytocin in producing tears in dogs. To do this, they asked human participants to rate photos of dog faces with artificial tears and other dogs with clear eyes. They also asked humans to rate how much they wanted to care for different dogs based on whether the dogs were crying.
“Photos of dogs with artificial tears ranked significantly higher than normal photos of dogs without tears,” the researchers noted.
“Unlike any other animal, dogs were evolved or domesticated through communication with humans and acquired advanced communication skills with humans through eye contact,” the researchers concluded.
“Through this process, their tears may play a role in triggering protective or nurturing behaviors in their hosts, thereby deepening mutual relationships and further promoting interspecies bonding,” they added in the paper.
