Have you ever wondered why some dogs are more aggressive than other dogs? Researcher, Evan MacLean, led a study set out to answer this question. MacLean studied two hormones, Oxytocin and Vasopressin (ADH), hormones that are also found in humans. Oxytocin, a hormone secreted by the posterior pituitary gland, sometimes labeled the “love hormone”, plays a major role in childbirth, nursing, and even found to play a role in bonding. On the other hand, Vasopressin (also secreted by the posterior pituitary gland), targets the kidneys and prevents loss of water.
MacLean gathered dogs from different age groups, breeds, and sexes whose owners reported aggression. Before experiment started, the dog’s hormones were measured. In the experiment, dogs were held on leashes while audio of a dog barking was played before revealing a dog model from behind a curtain; this was repeated again but with common noises and objects. After the various tests, the dog’s hormones were measured again and responses were noted. MacLean found that dogs that reacted aggressively had higher levels of Vasopressin, but they did not find a difference in levels of Oxytocin between the aggressive and non-aggressive dogs. This led researchers to measure amounts of oxytocin in assistance dogs compared to dogs in the study. They found that assistance dogs had higher levels of Oxytocin. MacLean also states that interactions between humans and dogs can release Oxytocin in dogs and humans.
Have you ever heard someone refer to their dogs as their “kids” or their “baby”? After reading this article, I can better understand this statement. Although this article was focused mainly on dog aggression I was surprised that human-dog interactions can lead to Oxytocin release in both parties, a hormone you would think is only relevant in adult human bonding and mother-infant bonding. The human response to release Oxytocin when interacting with a dog also helps me understand the use of therapy dogs for people with anxiety or other mental disorders. With all this in mind, the next time I hear someone refer to their dog as their kid maybe I won’t be as perplexed.
-Hanna Mathis
Reference:
University of Arizona. (2017, September 27). The hormone that could be making your dog aggressive discovered. ScienceDaily. Retrieved November 28, 2017 from http://www.sciencedaily.com/releases/2017/09/170927162032.htm
Original Research Article:
Maclean, E., Gesquiere, L., Gruen, M., Sherman, B., Martin, W. L., & Carter, C. S. (2017). Endogenous Oxytocin, Vasopressin and Aggression in Domestic Dogs. Frontiers in Psychology. doi:10.1101/151514
Biology In the news 
This is a very interesting article for me because dogs are my favorite animal. It is interesting to see that there are actual hormone level changes in dogs that show aggressive behaviors. I have read an article before how when dogs see their owner, they have oxytocin released, which is also stated in this article. I joke to my friends about how I don’t think I will ever love a person more than I love my dog, which now knowing oxytocin is released in response to my dog could actually be true for my strong bond with my dog.
Since there does seem to be a trend of higher Vasopressin in dogs that show aggression, I wonder if there is a study that could be done to counteract the increase of the hormone. Seeing so many dogs be put down or neglected from their aggressive behavior, the next question from this article is how can we change that?
This article didn’t necessarily change ideas in my mind, but it did open up the door of a reason behind the aggressive behavior in certain dogs. Dogs can have very different triggers to what makes them act in aggression, but if the overall process of why they are acting out of aggression is similar, than we can better understand how to combat the issue at hand.
This article that I found that was looking at a different approach to addressing dog aggression, which could produce faster results, was examined instead of the typical counter classical conditioning. https://www.whole-dog-journal.com/issues/11_5/features/Modifying-Aggressive-Dog-Behavior_16029-1.html. It would be interesting to use these techniques and measure the hormone levels before and after the treatment to see if there is an overall affect on the Vasopressin hormone and to see what produces the best affect.
-Allie Harper
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Hanna,
This post held my interest because even though I’ve never had a dog, I do like animals, and I find the endocrine system quite interesting. Although I am not surprised that dogs behave differently, I always assumed it was due to psychological scarring rather than hormonal processes. It seems that just like humans, the endocrine system of a dog functions quite similarly. However, since Vasopressin seems to be the cause of canine aggression, I must wonder if it is a series of issues that cause the increase in hormone level. For example, when the dog sees another dog and the fight response is initiated, does that decrease in blood flow to the internal organs impact the delivery of Vasopressin to the kidneys? Since all hormones travel through the blood, it would make sense that the two could be related. On the other hand, after learning that Oxytocin is the “love hormone,” it makes sense that the level is highest in canines when around their owner, due to the deep relationship present. Now that I think of it, I have also seemed perplexed in the past when hearing people refer to their pets in a childish way. One question I would like to ask the researchers though, is do the Epinephrine levels also relate to the aggression in dogs? Also, do you think these values and findings would hold up in different parts of the country? More trials could be completed in the future to test these additional factors.
Another student in our class, Abby, also wrote a blog post over the effects of Oxytocin in the body. She also speaks about how this hormone can promote relationships and good feelings. She talks about how higher levels of Oxytocin are present in the partner who “invests more” into the relationship. Do you think this could be true between dogs with the same owner as well? You can find her article here for further information:
https://biologyinthenewsblog.wordpress.com/2017/11/20/oxytocin-relationships/
Mallory Hasty
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The thing I found most interesting in this article was that Vasopressin plays a role in dog aggression. This surprised me because I wouldn’t expect that something involved in prevention of water loss would affect aggression. If I were to meet the scientists responsible for this work I would want to ask them what would happen with a lack of Oxytocin in the dogs or if they had any other ideas on things that would play into the aggression, for example if they think the way the dog was raised plays more of a role than the Vasopressin. I didn’t really have many impressions previous to reading this but as I read the title I thought that a decrease in Oxytocin increased aggression so it was surprising that it had nothing to do with it and obviously changed my mind on that idea. An article on the website, “The Spruce” talks about different causes of aggression and pretty much all of them are environmental factors, in fact the only cause they talk about that is not purely environmental is aggression as a result of illness. This article relates to the one on The Spruce as it could add value to the article and explain something most people with no background in the science behind dogs actions would never think of.
https://www.thespruce.com/top-causes-of-aggression-in-dogs-1117877
Allison Westbrook
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This is an interesting topic, for one, because when looking at oxytocin levels, we don’t usually relate them to human and dog relationships. The findings dealing with oxytocin did make sense, because I see that many people, including myself, can develop strong bonds with their pets–dogs, cats, and so on. It’s funny to see how scientists are discovering the extensive role of oxytocin in our lives and yet it’s affect is still vague. Another thing I found interesting about this article was the connection between ADH and dog aggression. I would not naturally assume any connection between the aggressive tendencies of dogs and higher ADH levels; this would be why I would want to ask the scientists conducting this experiment what their thoughts were as to how and if the hormone that deals with the prevention of water loss has a significant affect on the aggressiveness of dogs. Obviously, many other things must be taken into consideration for how aggressive a dog is–for example, it’s living environment–but the question of how that hormone plays a role in a dog’s personality is interesting. I would also want to learn more about how significant or insignificant oxytocin’s role is in the aggressiveness of dogs. Looking at this experiment, oxytocin does play a role, but once again, it’s significance is indefinite.
Abby White
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This is an interesting topic, for one, because when looking at oxytocin levels, we don’t usually relate them to human and dog relationships. The findings dealing with oxytocin did make sense, because I see that many people, including myself, can develop strong bonds with their pets–dogs, cats, and so on. It’s funny to see how scientists are still discovering the extensive role of oxytocin in our lives but how the significance of it’s affect is still vague. Another thing I found interesting about this article was the connection between ADH and dog aggression. I would not naturally assume any connection between the aggressive tendencies of dogs and higher ADH levels; this would be why I would want to ask the scientists conducting this experiment what their thoughts were as to how and if the hormone that deals with the prevention of water loss has a significant affect on the aggressiveness of dogs. Obviously, many other things must be taken into consideration for how aggressive a dog is–for example, it’s living environment–but the question of how that hormone plays a role in a dog’s personality is interesting. I would also want to learn more about how significant or insignificant oxytocin’s role is in the aggressiveness of dogs. Looking at this experiment, oxytocin does play a role, but once again, it’s significance is indefinite.
Abby White
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