Sunday, April 10, 2016

How Dogs Highjack Your Brain with Love Hormones

A little over 3 years ago, we rescued this puppy and named him Tolstoi. I have had dogs most of my life, so I have always taken for granted that special bond one has with a pet. However, Tolstoi is my husband's first dog, and watching that bond develop so quickly and so deeply was quite a special experience.

Dogs are wonderful in so many ways, and I've written about some of the ways dogs can enhance your health here. This week I thought I would share some recent #justplaincool research on the neuroscience behind the human-dog bond. 

There is a hormone in all mammal brains called oxytocin. Oxytocin is thought to play an important role in relationships. For example, oxytocin surges during cuddling and other intimate activities, in mothers when meeting their new infant for the first time, and while breastfeeding. I won't pretend that we fully understand the ins and out of oxytocin yet, but that's what makes science so exciting. 

Anyway, we have a pretty good understanding that the amount of oxytocin in your system fluctuates in ways that are salient to relationships, but so far those relationships have always been within the same species; human-human, rodent-rodent. Wouldn't it be cool if the neuroscience of how humans bonded with their dogs was dependent on the same processes through which humans bonded with other humans? Well, apparently that's exactly what happens. 

Dr. Miho Nagasawa, Azabu University, and her colleagues were interested in whether oxytocin in the body changes in humans and dogs when interacting with one another. To understand this, they recruited 55 healthy individuals and their dogs. All participants provided a urine sample and then were randomized to one of two conditions. Urine is one place you can measure oxytocin. In the first condition, participants were told to play with their dog for 30 minutes. In the other condition, participants were told not to look directly at their dog for 30 minutes. At the end of the 30 minute experimental condition, participants provided another urine sample. 

They found that the owners and their dogs that interacted during the 30 minutes showed large increases in oxytocin before and after the experiment. They also found that the largest increases in oxytocin occurred in owners who dogs initiated "gazes" with them frequently. This likely means that humans experience a similar neurochemical signal  when bonding with their dogs as with other humans, but that this signalling varies based on how much time owners and their dogs spend looking at eachother. 

My first thought when reading this finding was, well sure. Humans are very bonded with their dogs, and maybe surges of oxytocin just occur with humans interact with anything they are bonded with. Then I wondered whether the dogs experience this same surge in oxytocin. Luckily, Dr. Nagasawa has also conducted that study. 

In the 2nd study, they use the same procedure only this time they included a comparison group of hand-raised wolves and measured oxytocin in the urine of the canines in addition to their owners. They found that the increase in oxytocin after 30 minutes of interacting with their owner occurred in dogs but not wolves, and that the magnitude of oxytocin change was directly related to the length of time the owner and dog gazed at one another. 

Gazing is interesting for several reasons. We tend to take it for granted as a form of communication, but mutual gazing is considered the most fundamental manifestation of social attachment, especially between a mother and infant. Dogs and humans can't communicate verbally, so they rely on engaging socially with humans in other ways that tend to mirror how humans interact with their infant offspring. Another fun fact I learned from these articles was that dogs are apparently more skilled at using human social communicative behaviors than their will counterparts, wolves, but also chimpanzees. This suggests that dogs are uniquely capable of bonding with humans in ways no other species can.  

So basically, the next time Tolstoi stares at me, he communicating with me in a way that send natural "love drugs" throughout my brain to ensure I will keep taking care of him. Sneaky puppy, but man is it powerful. 

Unfortunately, some dogs havent been lucky enough to get rescued yet. If you want your brain highjacked with love hormones, some of these guys are up for the job. 

Nagasawa, M., Kikusui, T., Onaka, T., & Ohta, M. (2009). Dog's gaze at its owner increases owner's urinary oxytocin during social interaction. Hormones and Behavior, 55(3), 434-441.

Nagasawa, M., Mitsui, S., En, S., Ohtani, N., Ohta, M., Sakuma, Y., ... & Kikusui, T. (2015). Oxytocin-gaze positive loop and the coevolution of human-dog bonds. Science, 348(6232), 333-336.


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