Canine Companionship: Humans bond with dogs as if they are children

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Nothing is stronger than the bond between a mother and child... and between dog and human? Although I have not personally experienced motherhood, I recently added a new family member; a four-month-old rescue puppy named Linus (after one of my role models and great chemical engineers, Linus Pauling). When he looks into my eyes my heart melts a little, and I just want to scoop him up and hug him. These feelings are helping me understand why people refer to their dogs as “fur babies,” showering them with toys, treats, costumes, and even pushing them in strollers.

My new puppy, Linus

Now science explains why dogs really are “Man’s Best Friend.” When people refer to their dogs as their kids, they aren’t too far off. A new study in Science shows that humans and dogs actually share a unique bond, mediated through the love hormone, oxytocin. What makes dogs so special to us, and how did this symbiotic relationship begin?

Dogs were the first animal to be domesticated by humans

Image credit Dan Burr via Flickr

The dog-human relationship has a long history. Dogs were domesticated by humans before any other plant or animal, including food crops or livestock like horses and cattle. Scientists know that dogs evolved from the gray wolf, however they are still trying to figure out where and when they became friends with humans. The consensus among scientists is that dogs and humans began their relationship somewhere between 15,000 and 30,000 years ago during the Paleolithic era.

Charles Darwin, the man responsible for the theory of evolution, theorized that dogs initiated their relationship with humans, following them to scavenge their leftover animal carcasses and scraps. Eventually, dogs evolved to be more and more trusting of humans. The less fearful and friendlier dogs lived longer, evolving to become the human-like pets we know today that sit on our furniture, ride in cars, coexist (hopefully) with our other pets, and understand our language; although, we must remember they still have some wolf-like instincts from their ancient ancestors.

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Dogs have evolved to be the most responsive animal to human body language. For example, dogs are the only animal that understand what humans mean when they point at something with their hand - “look at that.” They respond to human cues and words, along with eye contact. Not even other primates can understand our complicated social cues to that extent. Why are dogs so unique in this aspect? A new study from researchers in Japan shows the feelings of companionship we have towards dogs are a result of direct eye contact.

Dogs manipulate the human feelings by staring at us

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When dogs and humans stare at each other, the love hormone, oxytocin, is produced. This relationship has evolved to create a bond between human and dog similar to the bond a mother and child have. Oxytocin is related to the feelings of love and comfort between humans, which you can read more about in this Valentine’s Day post. A new study by a group at Azabu University in Japan has linked the oxytocin hormone to the bond that humans and dogs have.

Increased levels of oxytocin are positively associated with increased social behavior towards both humans and other dogs. According to several studies, after dogs and their owners interact, oxytocin levels increased in both the dog and its owner. The Japanese researchers, however, showed that oxytocin increased the most after dogs and their owners share a mutual gaze for a sustained period of time, more than talking or touching.

To further solidify their findings, the researchers also artificially administered oxytocin to dogs and then had them interact with their owners. Dogs given oxytocin stared at their owners more than the dogs not administered oxytocin. Following the interaction, the dogs given oxytocin and their owners both showed an increased production of the hormone after the interaction. This suggests something known as a positive feedback loop, meaning that the more oxytocin present, the more gazing, and the more oxytocin is produced. In other words, it’s like a snowball effect, the more you and your dog stare at each other, the more love there is and the more you want to stare at each other.

A dog and owner gazing at each other

The special bond between a dog and its human is unique to its owner. Researchers also observed dogs interacting with humans who were not their owners, and oxytocin levels were unchanged. Not only is oxytocin production unique to the owner, it is unique to dogs as a species. Wolves reared by humans were studied along with their owners, and no relationship was observed between eye contact and oxytocin levels.

All of these observations suggest dogs have a unique neurological pathway specific to human bonding, which they have evolved over tens of thousands of years with us. They have also evolved to have adorable child-like characteristics to give us the “feels” for them, to put it unscientifically. These findings could also explain why aggressive behavior of dogs towards humans is correlated to their interactions with humans and not their breed. My only question is, why am I attached to my cat in a similar way, and when will he and my dog become friends?

For more information, check out this podcast from Science. 

Human health benefits from furry companions

Oxytocin is currently studied as a treatment for several mental disorders associated with decreased levels of the hormone. To treat these diseases, researchers are artificially administering oxytocin to improve social symptoms of disorders like autism and post-traumatic stress disorder (PTSD). Understanding how dogs can chemically alter our brains gives us an understanding of how and why service animals are beneficial. Assistance dogs can stimulate the production of oxytocin in people suffering from mental disorders.

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Oxytocin has also been studied to treat other mental disorders like depression, anxiety, and stress. More research is needed to understand more about this link, but for now I will take it as a sign to spend more quality time with my newest 4-legged friend, especially when I am stressed out. So at the end of the day, it might be mentally beneficial to take your furry friend on a walk or jog, play some ball, snuggle on the couch… or just stare at each other.

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Cheers to your brain and thanks for reading!

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Oxytocin: What is love?

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This Valentine’s day, you might be feeling extraordinarily giddy and happy with your main squeeze, or possibly a little irate or gloomy about not having someone to give candy and flowers. In any case, the concept of love has probably crossed your mind at some point today. What is love? Is there such a thing as “true love?” Will there ever be a person willing to put up with my annoying habits? The answer to these questions could lie in a hormone called oxytocin that is responsible for many of the emotions we feel associated with the word love.

What does oxytocin do?

Oxytocin is the reason we feel butterflies when the cute guy or girl across the room smiles at us. It is responsible for the warm fuzzy feelings we get when someone hugs us. It is also to blame for the sorrow and despair we feel when trust is broken.

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Oxytocin is also the reason for the strong maternal bond that humans have with their children. It is released during childbirth and breastfeeding. Most, if not all of oxytocin’s intended functions are related to human reproduction.

Oxytocin also has many medical uses because of its uplifting properties. It is sold synthetically under the name Pitocin to treat depression and to induce labor. Recently it has also been explored to treat autism after a study showed that people with autism displayed lower levels of the hormone than people without autism.

Oxytocin is one of the many hormones secreted by the pituitary gland. Hormones are produced in glands to tell your body to perform certain activities like digestion, growth, mood, and in the case of oxytocin, reproduction. When we do something that our bodies like, our brains release dopamine to make us feel good and tell us we should do it again. Dopamine is a neurotransmitter that can influence addictive behavior, outlined in last week’s post on sugar.

In the case of love and sex, dopamine triggers the release of oxytocin into the blood which binds with oxytocin receptors. When oxytocin binds it causes a strong bond to the person who caused the dopamine to be released (usually a sexual partner or baby). New research suggests that oxytocin is the reason that humans display monogamous behaviors in addition to maternal bonding. The video below does a great job of describing the relationship between love and the brain.

The reason for “til’ death do we part”

New studies have shown that oxytocin is responsible for monogomous relationship behavior in humans. Humans are one of the few species that exhibit monogamous behavior because from the standpoint of evolution it is advantageous for male species to spread their genes to as many partners as possible. Very little is known about the neurobiological reasons for humans to stay loyal to one sexual partner.

Another animal exhibiting monogamous behavior is the prairie vole. Studies on prairie voles have shown that oxytocin is released in the brain after mating. The voles form a partner bond with their mate after the interactions of dopamine and injected oxytocin. On the contrary, when female prairie voles were injected with an oxytocin antagonist they displayed no affection toward their male counterpart. 

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In a study done with 20 men, data revealed that oxytocin contributes to romantic connections by making them perceive their partner as more attractive than other women. After oxytocin treatment, the men perceived their partner to be increasingly attractive, displayed by a rise in neuroactivity. However, when shown pictures of unfamiliar women, there was no increase in neuroactivity. In other words, the pleasure areas of the brain lit up when they saw a picture of their partner, while pictures of the unfamiliar women showed suppressed feelings of pleasure.

Why would monogamy be beneficial to humans? Scientists think that the reason humans display pair bonding to their sexual partners is due to the decay in oxytocin over time in a relationship. Monogamy evolves in species because of the amount of work it takes to nurture offspring. Human offspring are more difficult to raise than other animals, so it took the work of two parents to raise a child when humans were evolving. Luckily in modern times, we have more access to resources to make raising children a possibility with one parent.

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Oxytocin is a strong and wonderful chemical. It makes us feel human. Whether or not you have a valentine today, go out there and make some oxytocin! Hug a friend, spend time with family, and get those feel-good fuzzies. Here’s to love!

Thanks for reading, and cheers to your brain!

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References:

Lee, Heon-Jin, Abbe H. Macbeth, and Jerome H. Pagani. "Oxytocin: the great facilitator of life." Progress in neurobiology 88.2 (2009): 127-151.

Scheele, Dirk, et al. "Oxytocin enhances brain reward system responses in men viewing the face of their female partner." Proceedings of the National Academy of Sciences 110.50 (2013): 20308-20313.