Oxytocin modulates responses to inequity in dogs.

Although several animals respond negatively to inequity, the underlying neurochemistry of the process remains poorly understood. In this study, we tested whether the neuropeptide oxytocin mediates responses to inequitable outcomes in domestic dogs (Canis familiaris). Subjects exchanged tokens to receive a food reward in conditions in which the distribution of reward varied. Dogs did respond negatively to inequity, refusing to participate in the test when their partner was rewarded and they were not. Their responses could not be explained merely by frustration, since the presence of a partner being rewarded had a significant effect on their behavior, compared to when the partner was present but not rewarded. Furthermore, after oxytocin intake dogs were less sensitive to the inequitable distribution of reward, performing more successful trials than when administered with placebo. Further, oxytocin treatment also increased dogs' attention towards their partners, and slowed their decision times, but did not affect their affiliation level towards their partners or the experimenter. Together, our findings suggest that oxytocin modulates responses to inequity in dogs by potentially affecting decision-making processes, but not by increasing affiliation.