Human interactions have a biochemical signature that is most evident in what happens between a mother and her baby. A study presented at the 12th International Conference on Human-Animal Interactions that took place this summer in Stockholm offers convincing evidence that the same biochemical process plays a role in the bond between dogs and their owners. Researchers Linda Handlin and Kerstin Uvnäs-Moberg of Sweden’s Karolinska Institute believe oxytocin is the “bonding hormone” that is released in humans and in dogs during mutual interactions. To test their theory, blood samples were taken from dogs and their owners before and during a petting session. “We had a basal blood sample, and there was nothing, and then we had the sample taken at one minute and three minutes, and you could see this beautiful peak of oxytocin,” said Uvnäs-Moberg in an interview on PBS. “The fascinating thing is, actually, that the peak level of oxytocin is similar to the one we see in breastfeeding mothers.”
The hormone oxytocin has a powerful physiological effect. It can reduce blood pressure, increase tolerance to pain, and reduce anxiety. Research indicates that owning a dog could even extend your life. “If you have a dog, you are much less likely to have a heart attack, and if you have a heart attack, you are three to four times more likely to survive it if you have a dog than if you don’t,” added Uvnäs-Moberg.
Oxytocin: The Baby-love Puppy-love Hormone
Oxytocin is a polypeptide hormone that has long been known to stimulate the contraction of the uterine muscles and the release of milk during breast-feeding. It is now recognized as an important modulator of the stress response. Stored in and released from neurons in the posterior pituitary as well as in the brain, oxytocin is synthesized in cell bodies of the magnocellular neurons located principally in the paraventricular nucleus of the hypothalamus. However, oxytocin is more ubiquitous as it is also synthesized in neurons that are widely distributed within the central nervous system. Oxytocin facilitates mother–infant interactions and tends to facilitate behaviors that oppose classic fight-or-flight behavioral responses to stress.
The Study: Dogs Have Feelings of Love, Too
Handlin and Uvnäs-Moberg sought to establish a correlation between levels of oxytocin and those of the stress hormone cortisol during interactions between dog owners and their dogs. Ten female dog owners were asked to evaluate the quality of their relationships with their dogs via a standardized questionnaire. They were also asked to interact with them, stroke them and talk to them for one hour. The owners’ oxytocin levels correlated significantly with questionnaire items indicating positive feelings and closeness to the dog, while cortisol levels were significantly correlated to items regarding negative feeling towards their dog. The dog’s oxytocin and cortisol levels also correlated significantly with the owners’ answers to items regarding their attitude toward the dog. The scientists concluded that hormones in both human and animal were related to the owners’ perception of their relationship with the dog. “A short-term sensory interaction between a dog and its owner [can] influence hormonal levels in both species,” says Uvnäs-Moberg. “The dogs’ oxytocin levels displayed a significant rise just three minutes after the start of the interaction. There was also a significant positive correlation between the dogs’ and the owners’ oxytocin levels after 15 minutes.”
