Magic Mustang Tamer

Does Oxytocin Create Trust?

It would be so convenient for us animal trainers if oxytocin explained trust. The oxytocin-trust literature is vast, you’ll never read it all, but Nave et al (2015) give us a framework to understand the human OXT-trust research. We will need this scaffolding to understand the animal OXY-trust literature.

Journal Reference: Nave, G., Camerer, C., & McCullough, M. (2015). Does oxytocin increase trust in humans? A critical review of research. Perspectives on Psychological Science, 10(6), 772-789.

Publication Date: 2015


Nave, Camerer, and McCullough examined the OXY-trust paradigm, surveyed the literature, and summarized the best evidence. They found reasons to be concerned about the scientific integrity of our understanding of the biosocial effects of OXY on humans. 


Most research on trust in humans is based on a straightforward game in which one player is given money that they can give or not give to a second player. If they give to the second player, the researcher triples the value given. Player Two can give money back to the Player One. The locus of the research is the willingness of Player One to let go of some cash.

And what will happen if they snort a little oxytocin before the game? That is the kind of question scientists were pondering in 2015.

Nave et al collapsed the field of study into three common approaches:

  1. Effect of application vs. placebo,
  2. Correlation of OXT level with a behavioral measure,
  3. Looking at genetic OXY variants effect on behaviors.

The trust game itself might be hard to do with an animal, but these three approaches are the same for all species. We’ll see that in the following papers where we look at OXY and horses.

List of typical problems in oxytocin-trust studies identified by Nave et al 2015.

  • Papers where oxytocin did not have an effect are unpublishable, but studies with surprising results are more often published. This creates a bias in the literature. About half of the published studies found effects of oxytocin.
  • It is difficult to measure OXY in the bloodstream (it must be extracted or cleaned). 
  • The power of detection of effects is limited. It requires large samples (Nave wants N=400) to get statistical significance.
  • There is a general failure to replicate most of these studies and many of them are exploratory without a null hypothesis to test.

From his critique, we can generate a checklist for the animal studies we will be reading.

  • uncheckedThe study started with a proper set of hypotheses.
  • uncheckedThe method to measure or deliver OXY seems legitimate.
  • uncheckedThe sample of animals is adequate for the question.
  • uncheckedThe statistics don’t involve a large number of variables but just those relevant to the hypothesis.

To counter the effect of such a down in the weeds-of-science report, I am going to tell you about a “study” that I did back in 2013, when everyone seemed to think oxytocin might be magic. You could order an oxytocin nasal spray called “Liquid Trust” so I did.

I had a mustang named Zarvona who spent his days snorting in fear. He understood the positive reinforcement games we played, but he would always go over-threshold into a total panic before long. I trained him to target the nasal spray container with a nostril, and then to hold his nose on the inhaler. I filmed that final step when a puff of oxytocin vapor squirts into the mustang’s nose and it looks pretty uneventful. He didn’t like the spray delivery and left in a huff but not a panic. No sign of him having a more positive appraisal of me.

This illustrates the difference between doing science-like things and doing real science. It was exploratory with no hypothesis whatsoever. Nasal spray is not a very effective means of delivering a drug to an animal with a large false septum. Sample size was small and no attempt was made to record any behavioral effects. We might learn something from exploratory work, but it is really not good science. We must remain skeptical.

Keywords: oxytocin trust science

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