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Oxytocin has ‘tend-and-defend functionality in group conflict across social vertebrates.

Scientists review the evolutionary history of oxytocin and its role in out-group conflicts.

Journal Reference: Triki, Z., Daughters, K., & De Dreu, C. K. (2022). Oxytocin has ‘tend-and-defend functionality in group conflict across social vertebrates. Philosophical Transactions of the Royal Society B, 377(1851), 20210137.

Publication Date: 2022


Triki et al reviewed the model of oxytocin’s role in group conflict participation across the animal kingdom. They presented a paradigm model combining ingroup and outgroup concerns, expected threats, and norm enforcement. The parameters, while quite heuristic, are not easy to assess across all social taxa.  However, the framework presented helps the animal trainer understand the factors modulating social decision making in the social animal.


There is nothing more fierce than a mother defending her new-born, but would it surprise you to know that the neurohormone making her fierce is the same one that elicits tender loving care? Dog, bear, donkey, rat… it’s the oxytocin talkin’. Triki and her coauthors review the role of oxytocin in “tending and defending” across the gamut of social species.

What are the drawbacks to promoting social bonding and trust in animal training? Will there be consequences we did not expect? In the human trust/oxytocin literature the dark side of oxytocin is well known, but these darker aspects have been rarely addressed in the animal research literature. What happens when we try to exploit the social decision-making network for our own objectives?

“The vertebrates witnessed the emergence of oxytocin and its sister nonapeptide vasopressin about 500 million years ago through gene duplication of a common ancestral gene, presumably in jawless fishes. Since then, the oxytocin structure has been highly preserved, from bony fishes to mammals, where the structural differences between oxytocin and its homologues and the recently discovered mammalian variants occur in one or two amino acids.”

Triki et. al, 2022

The authors parsed the willingness to participate in group defense into four components: the concern for in-group, the concern for out-group, the expectation of threat, and norm enforcement, then they looked at the literature for evidence how each component is affected by oxytocin. Surprisingly, every element EXCEPT out-group concern was amplified by oxytocin. Oxytocin doesn’t seem to stimulate aggression so much as it stimulates defense. Being a threat can trigger aggression, where otherwise, there would be none. It’s not that the oxytocin pushes the animal into xenophobia, it’s that the oxytocin makes defense so much more necessary.

Vasopressin, interestingly, is the more ancient molecule, and it regulates fluids in the body. There is some evidence for its involvement with the social decision making network, but not as explicitly as oxytocin. Both are synthesized in the hypothalamus and stored in the axons of the nerve cells. When released, oxytocin binds to specific receptors setting off a cascade of signals that rapidly modulate the social decision-making network. It then is released to the bloodstream, from which it is cleared out in urine and saliva. Fifteen minutes from being deployed, it is gone.

In animals oxytocin can be experimentally blocked or boosted. When it’s blocked maternal defense disappears, nests are not protected, bonds between partners become blurry, and fights break out within the in-group. When it is boosted, the animal stands watch over the nest longer and clings tighter to its mate and family. Boosted with oxytocin, our animal stands ready to defend and is less tolerant of threat.

As a trainer in search of trust, you might have considered boosting your animal’s oxytocin. How could we go wrong with the “love molecule”?  It is available over the counter in inhalers or in injectable form for helping that milkcow get through calving… but would you want to? How do you not be the “out-group” in the animal’s eyes? Who becomes the out-group?

I have personally tried boosting a couple of animals with a nasal oxytocin inhaler. My lack of results could reflect more technical delivery problems than lack of efficacy. I also wanted to know if oxytocin was responsible for the geldings dropping their penis during training. I learned only that science is harder than you think.

But I am left with some questions:

  • Are guard dogs oxytocin primed to defend their people?
  • Can an “in-group” include multiple species?
  • Can you diminish the perception of threat and become more socially relevant to the animal, or would amplification of bonding oxytocin also increase the apprehension of potential threat?

Keywords: oxytocin, vasopressin, trust, evolutionary biology, social decision-making network, affiliation, aggression

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