Care to share? Exploring the relationship between altruism and oxytocin in marmosets

Both human and nonhuman primates show the capacity to demonstrate other-regarding preferences, i.e., an understanding for the existence, benefit, and welfare of other individuals. However, the motivation or capacity to demonstrate other-regarding preferences, or to behave altruistically, depends on the social, cognitive, and neuroendocrine context. Oxytocin (OT) moderates the salience of social cues and affiliation toward others, but the extent to which OT facilitates altruistic behavior such as other-regarding preferences in nonhuman primates is currently unknown. Thus, the aim of this study was to use a Prosocial Choice Task (PCT) to evaluate whether 6 marmoset donors will altruistically provision food to familiar and unfamiliar partners. Additionally, I explored whether the manipulation of OT would influence the provisioning of food to familiar and unfamiliar partners. I found that marmosets preferentially rewarded unfamiliar partners but not familiar partners, which reveals marmosets’ capacity for other-regarding preferences. However, OT did not influence the proportion of altruistic tray pulling in the PCT or homecage grooming and proximity. These results suggest that marmosets are more sensitive to the payoffs of unfamiliar partners over familiar partners, but this effect occurred independent of OT manipulation. These findings highlight the importance of social context in understanding the motivation and demonstration for other-regarding preferences. However, more work is needed to uncover mechanisms and motivations for the marmosets’ stronger preference to reward unfamiliar partners more frequently than familiar partners