Inequity aversion strategies between marmosets are influenced by partner familiarity and sex but not by oxytocin

Abstract

Cooperation among individuals depends, in large part, on a sense of fairness. Many cooperating non-human primates (NHPs) show inequity aversion, (i.e., negative responses to unequal outcomes), and these responses toward inequity likely evolved as a means to preserve the advantages of cooperative relationships. However, marmosets (Callithrix spp.) tend to show little or no inequity aversion, despite the high occurrence of prosociality and cooperative-breeding in callitrichid monkeys. Oxytocin [OXT] has been implicated in a wide variety of social processes, but little is known about whether OXT modulates inequity aversion toward others. We used a tray pulling task to evaluate whether marmosets would donate superior rewards to their long-term pairmate or an opposite-sex stranger following OXT, OXT antagonist, and saline treatments. We found that marmosets show inequity aversion, and this inequity aversion is socially- and sex-specific. Male marmosets show inequity aversion toward their pairmates but not strangers, and female marmosets do not show inequity aversion. OXT treatments did not significantly influence inequity aversion in marmosets. While OXT may modulate prosocial preferences, the motivations underlying cooperative relationships, such as inequity aversion, are multifaceted. More research is needed to evaluate the evolutionary origins, biological processes, and social contexts that influence complex phenotypes like inequity aversion. Inequity aversion can differ within species in important and distinct ways including between individuals who do and do not share a cooperative relationship. Overall, these findings support the view that inequity aversion is an important behavioural strategy for the maintenance of cooperative relationships.

Oxytocin regulates reunion affiliation with a pairmate following social separation in marmosets

“…The social-context manipulations for both the long-separation (7 hr) and the short-separation (15 min) challenges were preceded by a 30-minsocial isolation for drug uptake(Figure 1). The data for these experiments were collected during earlier studies (Cavanaugh et al, 2016; Mustoe et al, 2015; Mustoe, Harnisch, Hochfelder, Cavanaugh, & French, 2016) and have not been previously published.…”

Oxytocin structure and function in New World monkeys: from pharmacology to behavior

“…2010); though OTA doesn’t always have this effect (Cavanaugh et al . 2014; Mustoe et al 2015; Mustoe et al . 2016).…”

“…(2014) found that Pro 8 -OT enhanced the amount of time spent in close proximity with their mate during a partner-preference test but in females only, while Leu 8 -OT had no effect for both males and females. However, the vast majority of findings in marmosets suggest that both OT ligands produce little to no effects on mate-directed behaviors including social approach, grooming, or huddling behaviors (all affiliative behaviors associated with pair-bond maintenance) (Cavanaugh et al 2014; Cavanaugh et al 2015); cooperative food sharing in a experimental prosocial food-sharing tasks (Mustoe et al 2015; Mustoe et al 2016); and affiliative behaviors (time in proximity, grooming, huddling) upon reunion following a long-term social separation (Cavanaugh et al unpubl data). While it would seem most likely that Pro 8 -OT treatments would produce larger effects on mate-directed behavior than Leu 8 -OT in marmosets, the data suggest there are minimal OT-specific effects.…”

“…F indicates effect was present in females, M indicates effect was present in males. Parenthetical “(undisturbed)” indicates observations were conducted in home cage without any other behavioral tasks. Superscripts indicate references: a Smith, et al 2010; b Cavanaugh, et al 2014; c Cavanaugh, et al 2015; d Mustoe,et al 2015; e Taylor & French 2015; f Cavanaugh, et al 2016; g Mustoe, et al 2016; h Taylor, Intorre, & French 2017; i Cavanaugh, et al unpubl data ; j Saito & Nakamura 2011 …”

Neuropeptide diversity and the regulation of social behavior in New World primates

“…The studies examining the effects of neuropeptides on social behavior in NWM are increasingly important because they repeatedly demonstrate that neuropeptides do not universally enhancing sociality and, in some cases, neuropeptides like OT have no significant influence on socially-relevant behavior (Mustoe et al, 2016). Rather these studies support the more nuanced view that neuropeptides alter sociality in ways that reflect species-specific social relationships and social contexts.…”