How Dogs Stole Our Hearts

If you are thinking that your dog is "your child of fur", then the science has his back. New research shows that when fellow dogs stare into our eyes, they activate the same hormonal response that binds us to human babies. The study - the first to demonstrate the effect of hormonal linkages between humans and other types - may help explain how dogs became our companions for thousands of years.

"It's an incredible discovery that indicates dogs have hijacked the human bonding system," says Brian Hare, a dog awareness expert at Duke University in Durham, North Carolina, who was not involved in the work. Hare says the discovery may lead to a better understanding of why service dogs help people with autism and post-traumatic stress disorder. "A repetition of this magnitude should be found because it is likely to have such far-reaching effects."

Dogs are already famous for their ability to interact with humans. Not only do walking and frisbee walk, fangs seem to understand us in a way that no other animal can understand. Point to something, for example, and your dog will look where you refer - an intuitive reading of our intentions ("I'm trying to show you something") that confuses our closest relative: the chimpanzee. People and dogs also see each other's eyes during the reaction - a sign of understanding and the emotion that close relatives of dogs and wolves interpret as hostility.

Also read: People Love Pets

It was this mutual view that aroused the interest of Takifumi Kikusui, an animal behavior at Azabu University in Sagamihara, Japan. The Kikusoy Lab studies oxytocin, a hormone that plays a role in the bonding of mothers, confidence and altruism. Other groups have shown that when a mother stares at her child's eyes, the child's oxytocin levels rise, causing the child to return to his mother's eyes, causing the mother to release more oxytocin, etc. A positive feedback loop appears to create a strong emotional bond between a mother and a child during a time when the child cannot express himself in other ways.

Kikusui - the owner of the dog for more than 15 years - asked if the same was true of fangs. 

“I love my dogs, and I always feel like they're more than a pet partner,” he says. So I began to wonder, "Why are they so close to humans?" Why are they in close contact with us? "

Kikusui and his colleagues persuaded 30 of their friends and neighbors to bring their pets to his laboratory. They also found a few people who were raising wolves as pets. When each owner of his animal was brought to the laboratory, the researchers collected urine from both of them and then asked his companions to interact with their animal in a room together for 30 minutes. During this time, owners were raising their animals and talking to them. The dogs and their owners also looked into each other's eyes, each other for two minutes, and each other for just a few seconds. (It was not surprising that the wolves communicated so much with their owners.) After the time was up, the team took urine samples again.

Mutual squinting had a profound effect on both dogs and their owners. Among the duo who spent the most time looking at each other's eyes, both males and females saw a 130% increase in oxytocin levels, and both males and females increased by 300%. (Kikusoy was one of them, taking part in the experiment himself with two standard poodle dogs, Anita and Jasmine.) The scientists saw no increase in oxytocin in dogs and owners who spent little time staring at each other, or on any of the duo wolf.

In a second experiment, the team repeated the same basic procedure, except this time they gave the dogs a nasal spray of oxytocin before they interacted with their companions. There were also no wolves this time. Kikusoy laughs: "It would be very dangerous to give the nose spray to the wolf." Female dogs giving nasal spray spent 150% more time looking at their owners, who in turn saw a 300% increase in oxytocin levels. No effect has been observed in male dogs or in dogs that are given nasal spray that contains only saline solution.

The results indicate that human-dog interactions provoke the same type of positive oxytocin feedback loop as seen between mothers and their babies, the team reported online today in Science. This, in turn, may explain why we feel so close to our dogs and vice versa. Kikusoy says that the nasal spray may have affected female dogs only because oxytocin plays a greater role in female reproduction, as it is important during labor and lactation.

He says that this positive feedback episode may have played a critical role in domesticating dogs. And since wolves turn into dogs, it is only those who can be associated with humans who receive care and protection. Humans themselves may have developed the ability to reciprocate and adapt the maternal feedback cycle to new species. "This is our biggest guess," Kikusoy says, suggesting that since oxytocin reduces anxiety, adaptation may be important to human survival as well. "If humans are less stressful, it is better for their health."

"I definitely think oxytocin is involved in domestication," says Jessica Oliva, Ph.D. A student at Monash University in Melbourne, Australia, whose work recently demonstrated that the hormone enhances dogs' ability to understand the human signal. However, she says, mutual stare does not happen in a vacuum; most of these dogs may associate the behavior with food and play, both of which can also boost oxytocin levels. Although we may view our dogs as our children, they do not necessarily see our mothers. We might just be great friends giving them a casual massage.