Dog-human chemistry: the role of oxytocin

Each person who shares their life with a dog is convinced of the uniqueness of their relationship, which is founded on unconditional loyalty and love. Yet, as with communication between cat and man, the mysterious alchemy between dog and owner could also have a scientific explanation. According to a recent study by researchers at Azabu University in Japan, a look between the quadruped and owner is enough to raise levels of a certain hormone in both of them that is responsible for driving the emotional bond between parent and child.

Oxytocin, the hormone that bonds species

Gestures of affection and meaningful looks are just a couple of the behaviours that are regulated by the human hormone oxytocin. Informally called the ‘love hormone’, oxytocin is credited with encouraging sociability among members of the same species and beyond. It is known for producing an immediate feeling of personal satisfaction and is especially important for driving the emotional bond between parent and offspring, which helps ensure continuity of the species. Knowing this crucial function, researchers from a Japanese team led by Miho Nagasawa set out to explore the relationship between humans and dogs to understand in detail how oxytocin might affect the interspecies bond.

The experiment: gazes, words and physical contact

The study started with the collection of urine samples from 21 pairs of dogs and their owners. The samples were examined before and after interaction that started with long gazes, followed by stroking then cuddling. The scientists found that there was an increase in the levels of oxytocin in dog and owner after each interaction. However, interactions based on eye contact between each pair produced significant increases of the hormone.

In the second phase of the experiment, the scientists administered oxytocin in the form of a nasal spray to some of the dogs, and an inert spray to others. The dogs were then put in to a room occupied by two strangers and the owner who had all been instructed not to have any physical contact with the dogs but to limit interaction to eye contact only. This time around, the females given the nasal spray gazed at their owners for significantly longer than the males, causing the owners’ oxytocin levels to spike by return. In comparison, the males that had been given oxytocin nasally increased their focus towards both the strangers and their masters. The scientist believe this difference in reaction between male and female dogs is probably due to the fact that oxytocin forms a key part in the bonding of mother and puppy; thus confirming the females’ natural predisposition to the care of their puppies.

When the first part of this experiment was repeated on wolves bred by humans however, the scientists didn’t find any evidence of oxytocin increase in the urine of dog or wolf as a result of the wolf-owner interactions.

In the light of these findings, the evolutionary explanation comes to our aid once again. It appears the long coexistence between dog and man has allowed the canine to evolve to take advantage of the human hormone oxytocin to blur the lines between the relationship between animal and owner to mimic that shared by parent and child. “These results suggest that humans may feel affection for their companion dogs similar to that felt toward human family members,” Dr Miho Nagasawa, from the department of animal science at Azabu University in Sagamihara, Japan confirmed.