Summary: New research on prairie voles demonstrates that oxytocin is not absolutely required for forming social bonds, but it is essential for forming them quickly and keeping those bonds stable. Voles without functioning oxytocin receptors took up to a week to develop peer preferences that normal voles form in a day, and in group situations they often failed to favor familiar companions over strangers.
Receptor-deficient voles also worked less to gain access to a companion and were less wary of unfamiliar conspecifics, indicating reduced social selectivity. These results point to oxytocin’s dual role: strengthening affiliation with trusted partners while supporting avoidance or rejection of outsiders.
Key Facts
- Bond formation speed: Oxytocin speeds the early formation of selective friendships.
- Social selectivity: Without oxytocin receptors, animals have trouble prioritizing familiar peers.
- Dual social role: Oxytocin affects both closeness to known partners and avoidance of unfamiliar individuals.
Source: UC Berkeley
New UC Berkeley research shows that oxytocin — often called the “love” or “cuddle” hormone — plays a key role in friendship formation.
Oxytocin is released during sex, childbirth, breastfeeding and social contact and contributes to feelings of attachment, trust and closeness. It is commonly linked to prosocial behaviors, though it can also be associated with aggression in certain contexts. Popular advice encourages boosting oxytocin through touch, music and exercise to support well-being.
Researchers often study prairie voles because, like humans, they form stable and selective social bonds. While many experiments focus on mating bonds, the Beery lab at UC Berkeley specializes in peer relationships—animal models of friendship—which can shed light on human conditions that affect social bonding, such as autism and schizophrenia.
Annaliese Beery, UC Berkeley associate professor of integrative biology and neuroscience and senior author of the study, and graduate student Alexis Black found that prairie voles lacking functional oxytocin receptors take longer to form peer bonds. Close vole friends typically huddle together, groom each other and sit in physical contact.
“Oxytocin appears especially important during the early phase of relationship formation and in shaping selectivity — for example, preferring a familiar individual over a stranger,” Beery said.
The genetically modified voles, produced in the UC San Francisco laboratory of collaborator Dr. Devanand Manoli, also showed reduced social reward: they exerted less effort to be near a friend and were less avoidant and less aggressive toward strangers.
“In short, oxytocin is less about how social an animal is overall and more about who it chooses to be social with,” Beery said.
The team also investigated how removing oxytocin receptors affected oxytocin release and availability using a novel oxytocin nanosensor developed with postdoctoral fellow Natsumi Komatsu and Professor Markita Landry. Those measurements helped reveal how feedback mechanisms and oxytocin signaling change when the receptor is absent.
The study was published Aug. 8 in the journal Current Biology.
What social voles tell us about social humans
Beery has focused on peer relationships in rodents because they offer an opportunity to dissect the neurobiology of friendship and compare it to other social relationships. She and colleagues also study social behavior and oxytocin receptor distribution across species, including South American rodents and North American ground squirrels, and have begun comparative field work across multiple vole species to determine which social traits are widespread versus species-specific.
Her team suspects that peer relationships may have evolved before monogamous mating systems in some lineages. In early trials, many vole species showed a preference for familiar peers, even though only a few species are monogamous, suggesting a deep-rooted tendency for selective social bonds.
Beery co-authored a 2023 study led by Manoli that questioned the long-held association between oxytocin and mating or parenting. That work showed prairie voles lacking oxytocin receptors still displayed monogamous mating and parenting behaviors comparable to normal voles, though other studies found those receptor-deficient voles take longer to establish bonds with mates.
To examine friendships specifically, Beery and Black ran three experiments comparing female prairie voles with and without oxytocin receptors.
First, they measured how quickly voles formed partner preferences. While wild-type voles typically form a strong preference for a familiar peer after about 24 hours of co-housing, oxytocin receptor-deficient voles showed no preference at that time point and required up to a week to develop a similar preference.
“Wild-type animals form a robust preference within a day, but null mutants show no sign of bonding after 24 hours; most catch up by a week,” Beery said. “So oxytocin isn’t required to form a relationship eventually, but it is critical for making that connection quickly and efficiently.”
Second, the researchers tested how stable established bonds remained in a group setting. Long-term paired wild-type voles tended to stay near known partners in a multi-room enclosure before gradually mingling with strangers. In contrast, receptor-deficient voles mixed freely and behaved as if they had no clear partner.
“It’s like going to a party: a wild-type vole would stick near a friend at first and then begin to mingle. The mutant voles didn’t show that initial preference,” Beery explained.
Third, the team measured the motivational value of social partners by requiring voles to press levers to access either a familiar individual or an unfamiliar one. Female wild-type voles pressed more for their partner in both peer and mate contexts. Mutant voles continued to press more for their mating partner but did not show increased effort for peer partners.
“These results suggest mate relationships may be more strongly tied to classical reward pathways, whereas oxytocin is especially important for the reward value of peer relationships,” Beery said.
Overall, lack of oxytocin signaling delays bond formation and reduces the stability and reward value of peer relationships, while also lowering avoidance and aggression toward strangers—highlighting oxytocin’s role on both the affiliative and the exclusionary sides of social selectivity.
Oxytocin nanosensors
To determine whether receptor loss changed oxytocin release, the team used a novel oxytocin sensor from Markita Landry’s lab. These sensors combine carbon nanotubes with selected single-stranded DNA that binds oxytocin and fluoresces, enabling detection of oxytocin release in specific brain regions.
Contrary to a compensatory increase, Komatsu and Landry found no excess oxytocin in the brains of receptor-deficient voles. Evoked oxytocin release was reduced and occurred at fewer sites in the nucleus accumbens, a key region involved in social reward across species.
Funding: Co-authors include Alexis Black, Natsumi Komatsu, Markita Landry, Jiaxuan Zhao, Scarlet Taskey and Nicole Serrano of UC Berkeley, Ruchira Sharma of UCSF, and Devanand Manoli. Beery’s work was supported by the National Science Foundation (CAREER award 2239635) and the National Institutes of Health (R01MH132908). Komatsu is now an assistant professor at the University of Illinois.
About this social neuroscience research news
Author: Robert Sanders
Source: UC Berkeley
Contact: Robert Sanders – UC Berkeley
Image: The image is credited to Neuroscience News
Original Research: Closed access. “Oxytocin receptors mediate social selectivity in prairie vole peer relationships” by Annaliese Beery et al., Current Biology. DOI: 10.1016/j.cub.2025.07.042
Abstract
Oxytocin receptors mediate social selectivity in prairie vole peer relationships
Friendships, or selective peer relationships, are a crucial part of healthy social functioning in humans, and impairments in these relationships are linked to adverse physical and mental health outcomes.
Prairie voles, like humans, form selective bonds with both peers and mates, making them a valuable model for studying the mechanisms of selective social attachment.
This study investigated the role of oxytocin receptors in peer attachment using female prairie voles lacking a functional oxytocin receptor gene (Oxtr1−/−).
We found that Oxtr1−/− animals showed significant delays in forming peer relationships compared with wild-type animals. Oxytocin receptor function also supported the maintenance of peer bonds, because Oxtr1−/− voles displayed reduced relationship stability and quickly lost selective attachments in a multi-chamber group-living environment.
Oxtr1−/− voles also exhibited deficits in general social reward and failed to show selective social reward for a peer partner over an unfamiliar conspecific. Evoked oxytocin release in the nucleus accumbens was reduced in both male and female Oxtr1−/− animals compared with wild-type counterparts, indicating no compensatory increase in oxytocinergic signaling.
Together, these findings indicate that oxytocin receptors influence the formation, persistence and reward value of peer relationships.