Benjamin A. Curry1, Brianne Donaldson2, Moana Vercoe1, Matthew Filippo3, & Paul J. Zak1,4
(1) Claremont Graduate University, (2) Monmouth College, (3) Western University of Health Sciences, (4) Loma Linda University Medical Center
Although many of us interact daily with animals, we have little understanding of how this affects our interactions with people. This study assessed the physiological effects of human-animal interactions and tested if this affected interpersonal trust. Participants (N=141) were assigned to play wit h a friendly but unfamiliar cat or dog for 10 minutes or to rest quietly in a private room. Blood was obtained from human participants before and after animal interactions or rest, and videos of animal interactions were coded for encounter styles. Participants then made interpersonal monetary decisions to quantify trust and trustworthiness toward strangers. Although oxytocin (OT) fell on average after interactions with both dogs and cats, there was a positive and significant correlation between the change in OT after interacting with a dog and lifetime pet exposure. Participants who had lived with four or more dogs in their lifetimes had a positive increase in OT after interacting with an unknown dog. We found a negative correlation between the change in OT after interacting with a cat and cat ownership. Participants who had a reduction in stress hormones after a dog interaction showed increased trust in strangers. Specifically, a one-percentage-point decrease in the stress hormone adrenocorticotropin hormone increased trust in a stranger by 24 percent. Our findings show that the human OT response to animals depends on previous pet exposure.