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Dog Mojo: Canine Gazes Change Our Biochemistry

Adoring looks from a dog affect owners to their very depths, causing them to release a love hormone.

A dog's loving gaze has incredible power -- changing human biochemistry for the better with a single look.

When a dog stares at a familiar friendly person and the person stares back, the hormone oxytocin spikes in both the canine and human, according to a new study, which helps to explain why the dog-human bond can be so strong.

The findings are published in the latest issue of the journal Science.

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"Oxytocin has many positive impacts on human physiology and psychology," senior author Takefumi Kikusui of Azabu University told Discovery News. "For example, it decreases blood pressure, and relieves stress and anxiety. We can really feel the warmth when we are with dogs...and it is feasible that dogs can feel the same sense of affection (from us)."

Kikusui, lead author Miho Nagasawa and their colleagues put 30 male and female dogs representing different breeds into a room with their owners for half an hour. During this time, the researchers documented every interaction between the dogs and humans, such as talking, touching and gazing. Measurements of oxytocin in the owners' and dogs' urine revealed that increased eye contact drove up levels of the hormone in the brains of both species.

The scientists conducted a near-identical experiment on wolves that had been raised by humans. The wolves showed no increase in oxytocin.

In yet another experiment, again with dogs and their owners, plus some human strangers, the researchers sprayed oxytocin directly into the noses of certain canines. Female dogs among this nose-sprayed group increased the amount of time that they gazed at their owners.

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Together, all of the findings support that there is an oxytocin feedback loop that occurs between dogs and their owners. Since oxytocin likely evolved to bond mammal parents with their infants, the researchers believe that the connection between many dogs and humans is comparable to parent-child bonding.

Because wolves experienced no oxytocin increases, even after happily playing with familiar friendly humans, Kikusui and his team think that dogs evolved the enhanced ability during their domestication. In fact, he said that "it is possible that dogs cleverly and unknowingly 'hijacked' the natural system meant for bonding a parent with his or her child."

Dog and human making a connection. | Mikako Mikura

Wolves probably get oxytocin spikes too, but only when interacting with their own kind.

Evan MacLean, an evolutionary anthropologist at Duke University, co-authored, with Brian Hare, a commentary piece on the new research. They suspect that when the wolf-like ancestor of dogs and wolves first encroached on human settlements, only the most docile individuals could approach humans fearlessly.

"What we know is that dogs today have many puppy-like characteristics of wolves, so in many ways they are baby-like their whole lives," MacLean told Discovery News.

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"Humans respond to infantile cues very sensitively," he added. "For example, look at how cartoons and stuffed animals are constructed (with) big eyes and big heads relative to their bodies. We have parental instincts toward most creatures that have juvenile characteristics, and that may be one of the keys for dogs winning our hearts."

Because oxytocin is found in all mammals, he and the other researchers believe it's possible that certain other animals living closely with humans, such as cats and horses, also promote the release of this hormone in their favorite people.

MacLean and Hare said the research could help to explain why individuals with conditions like autism and post-traumatic stress disorder benefit from assistance dogs. While oxytocin's role in the conditions is still debated, prior research has shown that this brain chemical, nicknamed the "love hormone," has its benefits.

A border terrier's loving eyes.

Facial expressions among social animals appear to have universal qualities, to the point where humans and other animals can discern how certain species feel just by looking at their faces. That's the suggestion in two new studies -- published in the Journal of Veterinary Behavior and PLOS ONE -- that help explain how humans can have such close, understanding relationships with animals such as dogs and horses, the subjects of the investigations. The research confirmed, through animal behavioral analysis, the underlying meaning of dog and horse facial expressions and also demonstrated that people have a natural knack for figuring out what they mean. For example, "this dog is experiencing a positive emotional state, as his owner has just come back," Emanuela Dalla Costa told Discovery News. She led both studies and is a researcher in the Department of Veterinary Science and Public Health at the Università degli Studi di Milano. She explained that the dog’s eyes are wide open, as is his mouth, yet his facial muscles are somewhat tense. Together, these features and others suggest that he is happy, eager and hopeful.

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Here is another happy dog. In this case, Dalla Costa explained, the dog's "lips are retracted, but with no exposure of the teeth." The dog is thrilled that its owner has just returned and eagerly looks to the human for guidance.

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This poor pooch "is tense, due to the departure of his owner," Dalla Costa said. Every part of the dog's face is turned in the direction of his owner's recent exit, maximizing the pup's ability to find him. The dog's eyes and tense mouth convey his worry and loneliness.

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This dog's gaze is riveted on its owner, who is holding food. "This emotional condition is considered positive, and we can assume that this dog is happy," said Dalla Costa, adding that "there is no visible tension in the facial muscles." Even though the eyes, ears and face are pointed in one direction, just as they were for the worried and lonely dog in the previous slide, this hopeful canine feels no anxiety.

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Every aspect of this dog’s face communicates concern and worry. "The mouth is opened and the dog is panting," Dalla Costa said. "The dog’s lips are partly drawn back, with no teeth exposure. The facial muscles show some degree of tension, visible through ridges that emerge on the lateral side of the face and near the eyes." His ears are up, yet not fully open, an indication that he’s attentive but also worried.

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If this dog could talk, the canine would likely be saying, "Oh, please -- feed me." The photo was snapped as the dog looked longingly at its owner, who was holding a favorite food treat. Dalla Costa explained that there is no visible tension in the dog’s face. Its expression cleverly communicates desire and gentleness, while also revealing a sense of hopeful expectation.

Horse expressions, meanwhile, share similar qualities with dogs. This horse, similar to the dogs happily looking at their owners, is attentive and awaiting direction. "The eyes are open and focused on the environment, ears are moving in the direction of sounds, and there is no muscle tension in the mouth," said Dalla Costa.

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This unfortunate horse was photographed while in pain, which, thankfully, turned out to be only temporary. In this moment, however, Dalla Costa noted that the horse's ears are in a sideways position. Its eyes are partially closed, and its "chewing muscles are strained and prominent." Even the horse’s nostrils are stiff over its tightly shut mouth.

While perhaps not as uncomfortable as the previous horse, this horse was also photographed while experiencing temporary, minor discomfort. In this case, the horse’s nostrils are wide open, while its lower lip is drawn back. Even its "ears are held passively backward," Dalla Costa said.

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This horse is completely relaxed. "There is no tension in the mouth and in the chewing muscles," said Dalla Costa. "The nostrils are relaxed." The horse was happy to be chilling out on a pleasant day in an open field.