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Man’s Best Friend? The Mysterious Role of Oxytocin Revealed


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The World of Dog revolves around humans. If you’re a companion dog, who you socialize with, when you frolic in the park, and whether or not you procreate are often determined by someone with two legs. Even if you’re a feral or village dog — and can do pretty much what you want — you wouldn’t say to your dog pals in “dogish”: “Hey guys, let’s pack it up and take it far, far away from those pesky humans.” Instead, village dogs live in close proximity to people, gaining access to our trash and waste. If you’re a street dog in Russia, you might even take the subway. Dogs benefit from hanging around us, so they do.

But do you ever wonder what makes some dogs so into us? Why at any moment Pluto might propel himself into Mickey’s arms, giving Mickey a full-on scrub-down with his tongue? Why some dogs want to meet everybody and anybody, while others would prefer you stay right where you are?

A recently published open access study — led by researchers from the Family Dog Project and Comparative Ethology Research Group, MTA-ELTE — used a novel methodology to investigate what mediates human-directed social behavior in dogs. The question posed by Kis et al. (2014) was: Could ‘human-directed social behavior’ in dogs be influenced by the dog’s oxytocin receptor (OXTR) gene?

Oxytocin Influences Dogs’ Friendliness?
Now, I know you know about oxytocin because everybody knows oxytocin. Maybe you’ve heard it described as the “love hormone” or even “The Most Amazing Molecule In The World” because of its involvement in social interactions, stress relief, and feelings of connectedness with other people. Spend time petting your dog, scratching Pluto’s body and ears, and you’re both apt to see increases in your plasma oxytocin levels, indicating a positive experience for you both. But oxytocin is also not simple. Ed Young points out in a 2012 Slate article: “The “love hormone” fosters trust and generosity in some situations but envy and bias in others, and it can produce opposite effects in different people.” Part of the story could be that variations in the gene that codes the oxytocin receptor mediate differences in social behavior.

How might you investigate whether Pluto’s exuberance for Mickey (and “people” in general) is somehow associated with Pluto’s genes? Here’s the approach Kis and colleagues took in their recently published study:

Step 1: Get to know the dog oxytocin receptor (OXTR) gene! For this study, the researchers selected two dog breeds, German Shepherds and Border Collies, and extracted DNA by swabbing the insides of their cheeks. This process ultimately identified three polymorphisms in the dog OXTR gene, with the incredibly easy names −212AG, 19131AG and rs8679684.

Step 2: Get a sense of how the dogs interact with people! Over 200 German Shepherds and Border Collies living as companion dogs participated in a series of standardized interactions with people. For example, the tests investigated how dogs greeted both known and unknown people, how dogs responded to a stranger approaching in a threatening manner, and how dogs responded when their owner hid behind a large tree (who doesn’t love playing hide-and-seek with dogs?).

Step 3: Bring dog genes and behavior together! The researchers examined whether there was a relationship between OXTR polymorphisms and how the dogs interacted with people on the social tests. They were particularly interested in how readily dogs approached people, as well as the dogs’ level of friendliness.

The Science Behind Pluto and Mickey
So where does Pluto’s people-directed friendliness come from? Lead author, Anna Kis explains, “The way dogs behave towards humans, at least among German Shepherds and Border Collies, is influenced by the oxytocin receptor gene.” For example, when it came to the -212AG polymorphism, both German Shepherds and Border Collies carrying the G allele showed less interest in being around people, suggesting the effect was the same in both breeds. But 19131AG and rs8679684 revealed opposite trends in the two breeds. For example, in the 19131AG polymorphism, “The presence of the A allele, as opposed to the G allele was associated with higher Friendliness scores in German Shepherds and lower Friendliness scores in Border Collies.” This opposite effect suggests that “other genetic and cellular mechanisms (unexplored in the present study) might play a role in the regulation of this behavior besides our candidate gene.”

Kis and colleagues are excited about this new direction, and rightfully so. This is the first study to suggest that dog sociality toward people is related to polymorphisms in the OXTR gene. “Oxytocin is often hailed as a ‘magic’ hormone,” Kis explains, “and research like this is finding that it’s part of a bigger system. This research is particularly interesting when speculating about the role of oxytocin in the evolution of social behavior.”

Next up for this line of research: replication and details on possible “mediating molecular mechanisms.” And while “it would be erroneous to assume that oxytocin broadly and invariably improves social cognition,” the current research expands our understanding of what could be contributing to the social behavior between two species, or why Pluto is sooooo into Mickey.

Maybe it’s not customary for a study to leave you with a song stuck in your head, let alone humming the 1962 hit single “Do You Love Me” by The Contours. But given this new line of research, it’s a pretty good fit. Looking forward to what comes next.

————–

Thanks to Anna Kis for discussion of this research.

Photo by Noël Zia Lee via Flickr Creative Commons.

References
Kis et al. 2014. Oxytocin Receptor Gene Polymorphisms Are Associated with Human Directed Social Behavior in Dogs (Canis familiaris). PLoS ONE 9(1): e83993
Odendaal, J., Meintjes, R.A., 2003. Neurophysiological correlates of af!liative behaviour between humans and dogs. Vet. J. 165, 296–301.
Young. E. One Molecule for Love, Morality, and Prosperity?

Julie Hecht About the Author: Julie Hecht is a canine behavioral researcher and science writer in New York City. She would really like to meet your dog. Follow on Twitter @DogSpies.

The views expressed are those of the author and are not necessarily those of Scientific American.





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