FLICKR, CRISTINA SOUZAWhen a pet dog looks into its owner’s eyes, the same hormonal response that bonds mothers to their infants is ignited, according to a study published this week (April 16) in Science. It’s the first evidence of a hormonal bond forming between different species.
“It’s an incredible finding that suggests that dogs have hijacked the human bonding system,” Brian Hare, an expert on canine cognition at Duke University in Durham, North Carolina, who was not involved in the work, told Science.
Dogs’ relationship with humans has long been known to be unique. Some have attributed it to humans’ long evolutionary history of companionship with domestic canines. This is undoubtedly a big part of the closeness the two species have attained, but what exactly supports that bond has remained unclear.
Animal behaviorist Takefumi Kikusui of Azabu University in Japan and his colleagues delved into this question by collecting urine from both dogs and their owners before and after 30 minutes of interaction between the two. The researchers found that those dog-owner pairs that spent the most time looking into each other’s eyes experienced a spike in oxytocin, a hormone known to influence maternal bonding in humans. Dogs that spent the greatest amount of time making eye contact had a 130-percent rise in oxytocin levels, while their owners had a 300-percent bump. Canines that spent very little time making eye contact with their owners experienced no increase in oxytocin. On the flip side, administering oxytocin to female dogs via a nasal spray increased the amount of time they spent looking into their owners’ eyes.
“The neural mechanisms present in all mammal species to promote the mother-infant bond have also been adapted to regulate bonding between mates,” Emory University’s Larry Young, who did not participate in the study, told Smithsonian Magazine. “Our work in prairie voles is an example. Oxytocin promotes the pair bond between monogamous mates. So it makes sense that this same mechanism could also be shaped during co-evolution of species where interspecies bonding occurs.”