Australasian Science: Australia's authority on science since 1938

Why We Can’t Resist Puppy Dog Eyes

By Magdeline Lum

Looking into the eyes of dogs activates the hormonal response that bonds adults to babies.

Dogs are renowned for their ability to interact with humans. There is an unspoken understanding between dogs and humans that is not matched by other human animal interactions.

For example, if you point at an object a dog will intuitively look at where you are pointing in an understanding that you are trying to show it something. This communication is not picked up by chimpanzees, which share 98% of the same DNA with us.

People and dogs also look into each other’s eyes while interacting. A wolf, the closest relatives of dogs, views this as a potential threat.

Science is beginning to unravel why people refer to their dogs as “furbabies”. The simple act of looking into the eyes of our four-legged friends activates the hormonal response that bonds adults to babies. Takefumi Kikusui of Azabu University in Japan has shown for the first time that this hormonal bonding effect can occur between humans and another species. It may also explain why dogs became companion animals.

The Kikusui laboratory’s main focus of study is how oxytocin plays a role in maternal bonding, trust and altruism. Research has shown that when a mother looks into her baby’s eyes, the baby’s oxytocin levels increase, causing the baby to look back into its mother’s eyes. This, in turn, causes the mother to release more oxytocin. This positive feedback loop creates an emotional bond between mother and child at a time when the child has a limited range of communication to express itself.

Being a dog-owner for more than 15 years, Kikusui wondered if this interaction held true for interactions between people and their canine friends. He and his colleagues approached and convinced 30 of their friends and neighbours to bring their pets into the laboratory. They were also able to find people who were raising wolves as pets, and invited them to be part of the study.

A urine sample was collected from both the owner and their pet before a 30-minute session of interaction. During this time, owners stroked their animals and talked to them. Dogs and their owners were observed to look into each other’s eyes for a duration lasting for a few seconds up to a couple of minutes. Wolves did not make much eye contact with their owners during these sessions. When the time was up, another urine sample was taken again.

What Kikusui and his team found was that the mutual gazing had an effect on both the dogs and their owners. For the pairs that spent the greatest amount of time looking into each other’s eyes, the dogs experienced a 130% increase in oxytocin levels and their owners had a 300% increase in oxytocin levels. There was no oxytocin increase in dogs and owners that had spent little time looking into each other’s eyes, and nor was there any in any of the wolf–human pairs.

The experiment was then repeated but this time the dogs were administered a nasal spray of oxytocin before interacting with their owners. There were no wolves involved in this part of the study. The female dogs in the study spent 150% more time looking into the eyes of their owners, who in turn experienced a 300% increase in their oxytocin levels. This effect was not observed in male dogs administered with an oxytocin spray or in dogs that were given a nasal spray that contained a saline solution.

These findings suggest that dogs have hijacked the human bonding mechanism. This may lead to a better understanding why service dogs are beneficial for people with autism or post-traumatic stress disorder, although this study does need to be replicated before any further conclusions can be arrived at.

The positive feedback loop demonstrated in Kikusui’s study may have played a key role in the domestication of dogs. As some wolves were evolving to dogs, only those that were able to bond with humans received care and protection, and humans evolved an ability to reciprocate by adapting the maternal bonding feedback loop to a different species.