Puppy-Dog Eyes Release Love Hormone

Puppy-Dog Eyes Release Love Hormone

Gazing between pets and owners neurologically strengthens their bond.

We all know that by looking into somebody’s eyes we can better understand this person’s attitude and intentions, and by protracting a mutual gaze we start establishing or we consolidate a bond. For example, gazing is important in deepening a relationship between a mother and her child, and between partners. Does the same apply to dogs gazing at their owners? Before we answer that question, let’s take a look at the science behind gazing.

The human gaze

Scientists have found that gazing activates neural circuits regulated by the molecule oxytocin. Oxytocin has subtle psychological effects that include enhancing feelings of social reward, security, trust, and decreasing anxiety. For example, a mother’s nurturing stimulates the release of oxytocin in her child, promoting the child’s attachment behavior, which in turn also activates oxytocin circuits in the mother, further inducing maternal care. In this way, a positive loop is established in which mutually induced oxycotin in the mother and her child strengthens the bond between them.

Anyone with a pet knows that caring for it builds a special relationship. In particular, this is true for dogs. They are able to develop a strong mutual attachment with their owners. Dogs not only enjoy being physically close and touching their owners, they can also establish and sustain eye contact with them. Usually when this happens, owners feel like their dogs are trying to tell them something. The question is, are the effects of gazing in human-dog relationships similar to those occurring in interactions between two people? Can mutual gazing activate similar brain circuits in people and dogs in a positive loop like the one described in a mother and her child?

The pet gaze

Nagasawa and colleagues of Azabu University in Japan have now answered these questions in an article published in Science this month.

The scientists examined a group of 30 volunteers with their dogs by measuring the duration of each dog’s gazing at its owner when the two were put together in a room and allowed to interact for 30 minutes. The results identified two groups of participants depending on the duration of the dog’s gaze: long gaze and short gaze. The researchers then measured the levels of urinary oxytocin at the end of the experiment and found that, in comparison with its levels before the analysis started, oxytocin was increased in both owners and dogs belonging to the long-gaze group. Thus, as in relationships between people, mutual gazing induces oxytocin during owner-dog interactions.

Interestingly, human-raised wolves, also examined in this study together with their owners, did not show any gazing behavior’. This indicates that gazing is not the result of being raised by humans, but rather, is an acquired trait that developed during evolution to facilitate social interactions. Wolves in fact usually avoid eye contact with humans and use gazing only as a threat toward other individuals of their species.

Experimenting with oxycotin

In a second experiment, the scientists administered oxytocin to dogs and then examined their behavior towards their owner as well as toward two unfamiliar people. They observed that exogenous oxytocin increased the duration of dogs’ gaze at their owners but not at the strangers, although this only occurred in female dogs. Indeed, exogenous oxytocin had no effects on the duration of male dogs’ gaze, neither at their owner, nor at strangers. Again, the longer gazing of female dogs induced oxytocin in the owners.

This second experiment thus confirms that oxytocin promotes attachment by stimulating behaviors like gazing that tend to strengthen bonds. As the researchers explain, in male dogs, exogenous oxytocin may have more complex effects and, for instance, activate other circuits that regulate aggression: in the presence of unfamiliar individuals these oxytocin-related circuits may alert dogs toward the strangers and divert them from trying to get closer to their owner. However, the scientists don’t mention whether exogenous oxytocin has an effect on male dogs gazing at their owners when no strangers are present.

Relationship evolution

This study shows that a biochemical mechanism active in relationships between people and involved in mutual recognition among individuals of the same species is also functional in relationships between people and dogs, i.e. in interspecies interactions. In other words, this study offers scientific proof that communication between people and dogs relies at least in part on neural circuits similar to those mediating interactions between people and, correspondingly, their activation can deepen the owner-dog connection.

The scientists suggest that dogs’ gazing behavior probably evolved during domestication and accompanied decreased fear and aggressiveness that facilitated cohabitation and interactions with humans. Thus, during evolution, humans and dogs acquired some similar neural traits that influenced their behavior, improving their social interactions and facilitating their mutual communication.

What about other pets, such as cats? Has this same mechanism also evolved in cats to some extent, but possibly cannot be as readily activated as in dogs?

As a cat lover, I’m convinced my cat tries to talk to me!

Nagasawa, M., Mitsui, S., En, S., Ohtani, N., Ohta, M., Sakuma, Y., Onaka, T., Mogi, K., & Kikusui, T. (2015). Oxytocin-gaze positive loop and the coevolution of human-dog bonds Science, 348 (6232), 333-336 DOI: 10.1126/science.1261022

Agnese Mariotti

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