A new study suggests that dogs and humans may have tapped into an instinctual bonding mechanism that originally evolved to reinforce the strongest biological bonds -- those between parent and offspring. In work reported in an open-access article published in the April 17, 2015 issue of Science, Dr. Miho Nagasawa from both Azabu University (Kanagawa, Japan) and Jichi Medical University (Tochigi, Japan) and colleagues from those institutions, as well as from the University of Tokyo, demonstrated that the hormone oxytocin, which spikes in both human and canine brains when the species interact, operates in a neural feedback loop that likely strengthened the bonds between man and his “best friend” for millennia. The researchers show that mutual gaze between the two -- an oxytocin-driven bonding mechanism known to strengthen emotional ties between human mothers and their infants -- helps to regulate the bonds between dogs and their owners as well. Because wolves don’t have this same response, even when they’ve been raised by humans, Dr. Nagasawa and colleagues suggest that this particular social bonding mechanism co-evolved in both dogs and humans over the course of the animals’ domestication. The researchers put dogs into a room with their owners, documenting every interaction between the two species, such as talking, touching, and gazing, for 30 minutes. They then measured oxytocin levels in the dogs’ and owners’ urine and discovered that increased eye contact between dogs and their owners had driven up levels of oxytocin in the brains of both species. In a second experiment, the researchers sprayed oxytocin directly into the noses of certain dogs and placed them in a room with their owners and some strangers. Female dogs responded to the treatment by increasing the amount of time they gazed at their owners.
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